Immunology Flashcards
(208 cards)
1
Q
What does the immune system enable?
A
The body to resist disease
2
Q
How does the body protect against pathogens?
A
There are physical barriers to protect against the entry of pathogens and if they fail that a cellular and chemical responses.
3
Q
What does the body detect?
A
The body must detect foreign ‘non-self’ antigens and distinguish them from the ‘self’ antigens in its own tissues.
4
Q
What have prevented pathogens from entering the body through a hole (eyes, ears, mouth, cut etc)?
A
Natural Barriers
5
Q
What is localised non-specific response?
A
When pathogens enter body tissue and try to reach the blood supply via capillary.
6
Q
What are the two localised non-specific responses?
A
Inflammation and phagocytosis
7
Q
What does inflammation cause?
A
Heat, redness, swelling and pain
8
Q
What are involved in phagocytosis?
A
Neutrophils and macrophages.
9
Q
What is the specific response?
A
When pathogens and the blood supply and can migrate around the body to target cells to reproduce.
10
Q
What are the cells responsible for the specific response.
A
B cells- Humoral response
T cells - Cell mediated response
Secondary immune defence - memory cells
11
Q
What is the first line of defence?
A
The natural barriers which try and prevent the entry of pathogens.
12
Q
How does the eyes protect and prevent the entry of pathogens?
A
As they produce tears which contain antibodies and lysozyme (lysozyme is an enzyme which hydrolyses peptidoglycan)
13
Q
How does the skin flora protect and prevent the entry of pathogens?
A
It comprises bacteria and fungi which outcompete pathogenic strains.They are not easily washed off so regular washing is important in resisting infection. Microflora prevents pathogens from colonising.
14
Q
How does the skin protect and prevent the entry of pathogens?
A
You have a layer of the epidermis contains dead keratinised cells – keratinocytes act as a physical barrier to pathogens. Keratin makes the skin waterproof.
15
Q
How does the ears protect and prevent the entry of pathogens?
A
It produces wax which traps pathogens and lysozymes
16
Q
How does the respiratory tract protect and prevent the entry of pathogens?
A
Ciliated cells what make is the top of the trachea where it is swallowed and passes into the stomach which contains acid (pH two), the lining is made of ciliated epithelium cells.
17
Q
How does the urethra protect and prevent the entry of pathogens?
A
Flow of urine
18
Q
How does the mouth protect and prevent the entry of pathogens?
A
Lysozyme is present in the saliva
19
Q
How does the vagina protect and prevent the entry of pathogens?
A
Acidic and mucus
20
Q
How does the stomach protect and prevent the entry of pathogens?
A
Stomach acid kills many microbes which are ingested in food and drink.
21
Q
What do you ciliated mucous membranes do?
A
The sticky mucus lines the passages and traps pathogens. This is found in the gut, genital areas, anus, ears, nose and respiratory passages.
22
Q
What does resistant disease also depend on?
A
Someone’s general health and diet.
23
Q
What happens if someone is deficient in vitamin C?
A
It can lead to weakened connective tissue causing open wounds. As vitamin C is essential for the synthesis of collagen which makes skin tough.
24
Q
What is the second line of defence?
A
Non-specific response
25
What does the second line of defence do?
The barriers try to kill any pathogens which have entered the body and stop them spreading.
26
What does localised defence involve?
Inflammation and phagocytosis which localises are breaking the barrier and destroyed invading micro organisms (pathogens)
27
What is inflammation?
It is a defence mechanism when there is a damage to the tissue.
28
What happens to the blood flow during inflammation?
There is an increase in blood flow towards the site of infection which bring a large number of phagocytic cells. The broken capillaries heal and the rise in temperature is unfavourable to microbes.
29
What are the functions of inflammation?
To destroy the cause of infection.
Limit the effects on the body by confining the infection to a small area.
To replace or repair damaged tissue.
30
Describe the process of phagocytosis.
1. There is an increase in diameter and permeability of blood vessels in the damaged area with blood flow increasing.
2. Blood clots forming damaged blood vessels. Approximate one hour after infection phagocytes reach the infection and performs of phagocytosis. After a few days an abscess full form which contains dead phagocytes, damaged cells and bodily fluids (past). New cells will be produced by mitosis in order to repair the damage tissue.
31
What are the two different types of non-specific white blood cells which are produced in the bone marrow and what do they do?
Neutrophils and macrophages. They engulf and digest foreign particles to at the body.
32
Tell me about neutrophils?
The number increases as a result of the infection.
Then engulf and destroy pathogens.
They are short lived – tend to die after engulf in the bacteria. Identified by my multi lobed nucleus, sausage like nucleus.
33
Tell me about macrophages
They settle in the lymph nodes, spleen and kidney. Then engulf pathogens and present antigens on the surface (antigen presentation).
Long lived – survive after golfing bacteria. It's important and stimulating the specific immune response.
Bean shaped nucleus.
34
What are antigens?
They are molecules which the body can generate a response to (generating an antibody response).
They are large with many being proteins. They are found on the pathogen surface.
35
What happens if the immune response system recognises antigens?
Then they are foreign to the immune system so a immune response is stimulated.
36
What sort of molecules can antigens be ?
Proteins, polysaccharides or glycoprotein molecules.
37
Describe the shape of antigen?
So the antibody will have a specific/complimentary shape which can recognise them so the antigens have a specific shape to. Antigen is a found on the surface of bacteria or viruses as well as cell surface of foreign tissue such as organ transplants or transfused blood cells. Each pathogen has its own unique antigens which are genetically determined.
38
What can be released by microbes?
Toxins
39
When are antibodies produced?
They are produced when antigens are present as its the immune systems way of responding to the antigen.
40
Describe the shape of antibodies?
They have a specific shape which is complimentary to that particular antigen. Quaternary structure with 2 heavy and 2 light chains.
41
What is an antibody?
Antibodies are large protein molecules which detect and neutralise antigens, they are released in the blood.
42
What can antibodies also be known as?
Immunoglobulins e.g IgG, IgA
43
Describe agglutination?
Each antibody has got more than one binding site so I can stick to more than one antigen. Forming antibodies – antigen complexes so the pathogens are held in large clumps. Macrophages and neutrophils can more easily engulf pathogens which are immobilised by agglutination.
44
Describe neutralisation.
Antibodies stick to the antigens which is useful for when toxins are released, antibodies will stop the antigens from getting around and stop it sticking to other parts of the body so other targets.
45
Describe opsonisation?
Once an antibody has stuck to the antigen there is many constant regions which stick out. This process enables the identification of the invading particle to the phagocyte.
46
Why do phagocytes have receptors on the surface?
So they can bind to the constant region of the antigen.
47
What happens if something is stuck on an antibody?
It has to be a foreign invader as antibodies are only produced when something foreign has invaded which can be destroyed by phagocytosis.
48
When is the specific immune response used?
If a pathogen invades the body immune system must respond with the specific new response being a response of any type of pathogen antigenic lymphocytes. An antigenic response which involves lymphocytes is known as the specific immune response. It occurs as the antigen is recognised as foreign to the body.
49
What are lymphocytes?
They derived from stem cells in the bone marrow and their precise role depends on their subsequent location. These cells are found in the immune system. They are white blood cells with a large nucleus with a little cytoplasm. They are produced before birth and are involved in the immune response. They are stimulated by a particular antigen in order to perform their function.
50
What are the two types of lymphocytes?
B lymphocytes and T lymphocytes
51
What response does B-lymphocytes have?
Humoral response - First response to produce antibodies.
52
What response does T-lymphocytes have?
Cell mediated- Response with cells doing the job of getting rid of the pathogens. It does it's job via direct contact.
53
Describe the similarities between B and T lymphocytes?
They are produced by stem cells in the bone marrow (immature cells are made in the bone marrow with mature cells found at different parts of the body) they have surface receptors which help them identify pathogens/antigens which to respond to. They look the same.
54
Where do you B lymphocytes mature?
They develop and are 'educated' in the bone marrow and migrate to the lymph nodes where they can count antigens.
They mature in the spleen and lymph nodes (collection of tissue)
55
What do B lymphocytes develop into?
Plasma B cells - secrete antibodies.
Memory B cells - remain dormant in the circulation and then divide to form more B-lymphocytes if the same antigen is encountered in the future. They remain in the body for years and act as an immunological memory.
56
How do the lymphocytes start?
They will start as B-lymphocyte and if activated they will produce antibodies with a cytoplasm swelling up as they have more ER which will secrete antibodies.
57
Where does the T lymphocytes migrate and mature?
They migrate to the thymus gland to mature from the bone marrow and undergo thymic 'education'
58
What do you T lymphocytes develop into?
T helper cells which release cytokines which stimulate B lymphocytes to develop and stimulate phagocytosis (they control the immune system). They activate T killer cells.
T killer cells attack and kill infected cells. Cytotoxic lymphocytes destroy target cells and contact it kills them by cell lysis.
T suppressor cells switch off the immune system after it's been switched on. It switches off when the antigen has been cleared and prevents inappropriate activation by self antigen.
T memory cells help generate a faster response.
59
What does cytokines stimulate?
Phagocytic cells e.g. macrophages, monocytes and neutrophils to engulf pathogens and digest them.
60
What are T cells selected on?
The ability to recognise pathogens (nonself) and to ignore host (self) tissue.
61
Where do naive T cells encounter antigens?
In the lymph nodes.
62
What does immune system respond to?
Any antigens whilst ignoring the bodies antigens and ignoring our microflora. Immune system must be able to recognise self antigens. A body cells have antigens on the surface which acts as a molecular identification unit each person.
63
What happens if a cell responds to it self antigens?
It is soon deleted out of formation otherwise the cell would think that its own body cells need to be destroyed initiating an autoimmune response (where the body attacks its own cells).
64
Why are B and T cells specific?
As each one responds to a different antigen this is because of genetic recombination when they mature.
65
Why do you sometimes develop symptoms when suffering from a disease?
As only one B and one T-cell can respond to a specific antigen it takes a long time to find them so much than increasing number. This means you may suffer from the disease. It takes a few days for this specific immune response to clear the infection and then you start to feel better.
66
What is clonal selection
It's a process at which a single B or T cell which recognises an antigen which has entered the body is selected from the pre-existing cell pool of different different antigen-specificities.
67
Describe the process of clonal selection.
A pathogen enters the body and produces toxins. Macrophages perform phagocytosis and antigen presentation.
Macrophage must find one specific B and one specific T cell which has a complementary receptor that can bind to the antigen.
The antigen binding to the complementary receptor on the membrane of a specific T or B activates the cell.
68
What is clonal expansion?
Dividing repeatedly into genetically identical cells (daughter cells formed through parent cells) forming a large population of cells specific to a particular antigen. This is created by mitosis.
69
What is cell differentiation?
When the cells can differentiate into various classes of lymphocyte i.e. plasma cells, memory cells and T cells
70
Once a T cells clonally selected it can differentiate into what type of cells?
Cytotoxic (killer) T cells – destroy infected cells.
Helper T cells – cytokines stimulate B cells to develop and phagocytes to be more active.
Memory T cells – respond if the pathogen enters the body again.
Cell mediated response
71
Once a B cells clonally selected it can differentiate into what type of cells?
Plasma B cells – produce antibodies which are specific to the antigen – humoral response.
Memory B cells – remain in the body for years and respond if the pathogen enters again.
72
Describe the primary immune response
When a pathogen enters the body the time it takes for cloned plasma B cells which secrete antibodies complementary to the pathogen is antigen is long.
It requires self expansion of T helper cells which secrete cytokines required to promote cell growth.
The antibody level will rise in the blood however a delay causes the person to suffer from the disease, the plasma B cells secrete antibodies for about three weeks.
Once a pathogen is eliminated the antibody levels in the blood will fall.
Specific memory B and T cells will remain.
73
In the primary immune response is the latent period short or long?
It has a short latent period in which macrophages engulf the foreign antigen to which is attached and incorporated by antigenic molecules into their own cell membranes which is called antigen presentation.
74
What sort of cell are macrophages?
Antigen presentation cells
75
Describe the secondary immune response?
If the pathogen re-invades the body the memory B cells clone rapidly to produce more antibodies more quickly (this cell clones will proliferate). The latent period is dramatically reduced. Antibodies are produced over a shorter period of time and they are up to 100 times more concentrated than the primary response. The secondary immune response relies on memory cells and protect against an identical antigen.
76
What do memory B cells turn into?
Plasma B cells
77
What is the concentration like for antibodies in the secondary immune response?
Antibodies remain high concentrations in circulation for longer and no symptoms develop.
78
What is active immunity?
It's when the body makes its own antibodies stimulated either by an infection or vaccination.The protection is long-lasting due to the production of antigen specific memory cells.
79
What is natural active immunity?
This is when lymphocytes are active by antigens present on pathogens.This takes place during the natural cause of infection. Both memory B and T cells are generated.
80
What is artificial active immunity?
A vaccination is given to raise an immune response – this contains antigens from the pathogen which initiates a response from production of memory cells (the cell mediated and humoral responses are initiated).
81
What does a vaccine cause?
A deliberate exposure to harmless antigenic material to activate and then you response and antibodies and memory B cells which provides immunity.
82
Give the history of the vaccine
Edward Jenner gave the first vaccination to a child who he vaccinated who had cox pox. Before subsequently infecting him with smallpox. The child seemed resistant to smallpox.
83
What sort of vaccines can you get?
Weakened or attenuated vaccines – they don't cause a disease e.g. measles, mumps and rubella.
Dead microorganisms – contain antigens e.g diphtheria. Purified antigens – created by genetic engineering e.g. hepatitis B.
84
What is the vaccine recognised as?
It's recognised by the body as non-self and immune system behaves as if it would if a pathogen was present this is active immunity as the body is producing its own antibodies.
85
Why are boosters given?
Overturn the number of memory cells will decrease if not expose the antigen again. So bases are given to give further exposure creating faster, bigger and longer lasting response than before. Memory cells are then produced again so many more come protect the body for longer.
86
Why is it beneficial that pathogens exhibit none or low levels of antigenic variation?
As they are more likely to be protected by single round of immunisation e.g. rubella then an organism that has many antigenic types and mutates frequently e.g. influenza so requires frequent exposure.
87
What are the ethical considerations when designing vaccines?
```
Potential side-effects
Effectiveness
Risk posed by the disease
Cost of the vaccine program
Religious concerns
Civil liberties.
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88
What is artificial passive immunity?
When a pre-synthesise antibody is injected into an individual e.g. e.g. tetanus antitoxin, rabies.
It provides a rapid immune response if there is no time for the active immune response to develop.
It provides short-term protection as antibodies are destroyed by phagocytes in the spleen and liver.
No memory cells are produced.
89
Give an example of artificial passive immunity?
Rabies (viral disease which affects animals and humans). It causes inflammation of the brain, fever, nausea, vomiting and results in death if untreated. Treatment: injection with immunoglobulins which bind to and neutralise the virus.
90
What is natural passive immunity?
It's when the body receives antibodies produced by another individual this happens when:
The mother passes antibodies to the foetus via the placenta.
The mother passes antibodies to the baby via breast milk. Colostrum (first breast milk) contains high levels of IgA which is absorbed in the blood.
It provides short term immunity as the antibodies are quickly destroyed by the host.
91
What are the features of prokaryotes?
No membrane bound organelles.
No membrane bound nucleus – circular DNA free in the cytoplasm (found in the nucleoid) and many small additional circular pieces of DNA called plasmids. Smaller ribosomes and eukaryotes.
Peptidoglycan cell wall.
They're generally very small (0. 5–5 micro meters)
They reproduce by binary fission
92
What is the name of the bacteria which is rod shaped?
Bacillus
93
What is the name of the bacteria which is spherical?
Coccus
94
What is the name of the bacteria which is spiral?
Spiral
95
What can bacteria be classified by?
It can be classified by whether the cell wall can take up a gram stain.
96
What does the gram stain depend on?
The cell wall structure
97
What colour does a gram positive stain?
Purple
98
What colour does a gram negative stain?
Pink
99
Describe the structure of bacterial walls?
The cell wall is made from peptidoglycan which consist of molecules of polysaccharides cross-linked by amino acid side chains. The cross-linking provides strength and the wall protects against osmotic lysis. The presence of extra layer protects the cells from the action of the antibacterial agents such as lysozyme and penicillin. It is surrounded by an outer layer of lipoprotein and lipopolysaccharide
100
Describe the structure of gram-positive bacteria?
These bacteria have a thick peptidoglycan layer which makes up 90% of the cell wall. Peptidoglycan is accessible to molecules outside the cell making it acceptable to attack by lysozyme and penicillin.
101
Explain the colourisation of a gram-positive bacteria?
Pores in the murein close during the decolourisation stage of the Gram stain protocol and so crystal violet is retained within the cell which stains purple. Safranin is used as a counterstain intensive violet grams positive cells purple.
102
Give an example of a gram-positive bacteria?
Staphylococcus (MRSA) – penicillin is affective against gram-positive bacteria as it weakens a cell wall causing the cell to burst due to osmotic lysis.
103
Describe the structure of gram-negative bacteria?
It has a thin layer of peptidoglycan (no more than 10% of the cell wall) it also has a protective outer layer of lipopolysaccharide and lipoprotein outside the cell wall. The lipid outer layers protect murein from antimicrobial agents including lysozyme on penicillin.
104
Explain the colourisation of a gram-negative bacteria?
During a gram staining the crystal violet is not retained within the cell wall so when it is washed off it takes a pink counterstain.
105
Give an example of a gram-negative bacteria?
E. coli – penicillin is not affective against gram-negative bacteria as a cell wall is resistant due to the lipopolysaccharide layer (this can be controlled within the antibiotic tetracycline).
106
Describe E. coli?
Rod shaped
Pink/red = gram negative
Found in the gut- produce vitamin k and protect by outcompeting pathogens
107
Describe B subtilis?
Rod shaped
Purple=. gram positive
Naturally found in the soil and vegetation
108
What are antimicrobials?
Compounds which inhibit bacterial growth. They are: Antiseptics uses on living tissue e.g. Dettol.
Disinfectants used non-on nonliving surfaces e.g. bleach.
Antibiotics.
109
What are antibiotics?
Antibiotics are chemicals produced by fungi and bacteria to interfere with the by chemistry (care of competition). They are use medically to affect the bacterial metabolism but not the host cells metabolism. They can be used without harming human cells because they target molecules in the bacterium which are different to ours.
110
What can't be treated with antibiotics?
Viruses as they are not affected due to the absence of metabolic pathways. Then multiplying take over human cells (any toxic chemical acting against him could affect normal cells) I need bacterial diseases can be treated with antibiotics.
111
What do bactericidal antibiotics do?
They kill bacteria
112
What do bacteriostatic antibiotics do?
They prevent bacterial multiplication (growth) but doesn't cause death. It's loads of stops bacteria growth, once the antibiotics are no longer present then the bacteria's metabolism will resume
113
What are the two main types of antibiotics?
Narrow spectrum and broad spectrum.
114
What is broad-spectrum?
It's affective against a wide range of pathogenic bacteria. It kills many types both positive and negative bacteria. They usually affect common processes like protein synthesis.
115
What is narrow spectrum?
It's when antibiotics are only effective (kills) against certain types of bacteria
116
What antibiotic is penicillin?
It is a narrow spectrum and bactericidal. It kills gram-positive bacteria as its more effective against gram-positive than gram-negative due to the differences in the cell wall.
117
Describe how penicillin works?
It resonate a fuse through the cell wall of the bacteria through Porins (surface molecules). Bacteria continuously makes and breaks down parts of the cell wall. The enzyme DD transpeptidase catalyses and breaks down the crust think is found between the amino acid side change joining peptidoglycan molecules.
Penicillin affects the formation of cross linkages in the cell wall during growth and division of bacterial cells. It binds to an inhibits the enzyme is responsible for the formation of cross links between peptidoglycan molecules. The wall as we can so when osmotic changes occur, cells lyse as the wall is too weak to withstand increase pressure potential.
118
How much of the bacteria is affected by penicillin?
As it is so small it can penetrate through the whole of the cell wall so all is affected. Weakening the cell wall makes the bacterium vulnerable to attacks by antibodies and enzymes e.g. lysozyme
119
Why are gram-negative bacteria not affected by penicillin?
As it is protected by a lipoprotein outer layer and polysaccharide.
120
What is tetracycline?
The fungus streptomyces produces tetracycline a broad spectrum antibiotic. It also is bacteriostatic. It acts against gram-positive and gram-negative so has a wide medical use against the bacteria that causes acne, infections e.g. chlamydia and against where diseases e.g. anthrax and the plague.
121
How does tetracycline work?
It prevents translation of mRNA during protein synthesis (stops the cells manufacturing new proteins like enzymes). It both diffuses and is pumped into bacterial cells. This antibiotic affects protein synthesis, a common metabolic process. It acts by competitively inhibiting the second anti-coding site on the 30S subunit of the bacterial ribosome and prevents the binding of the tRNA molecule to its complementary codon. Tetracycline inhibits the translation stage of the protein synthesis.
122
How do you know that tetracycline is bacteriostatic?
As it binds reversibly, it slows down population grow so can't make proteins, divide or increase the number. As the immune system now has time to find and destroy the bacteria.
123
What is the antibiotic sensitivity test?
It's a test carried out to find the most appropriate antibiotics to use in a bacterial infection
124
What type of antibiotic does chloramphenicol affect?
Bacteriostatic and broad spectrum
125
What is antibiotic resistance?
It is when a microorganism that has been previously susceptible to an antibiotic is no longer affected by it.
126
Why does antibiotic resistance occur?
Bacteria so genetic variation in their resistance to antibiotics this could be a result of a random mutation during DNA replication.
Resistant bacteria can pass their DNA (resistant strains) to non-resistant ones during sexual reproduction through conjunction by pili
127
How does the antibiotic act as a selection agent?
As when it is given the bacteria which isn't resistant dies and the ones that are resistant survives.
128
Describe how antibiotic resistance can occur when the antibiotic acts as a selection agent?
They're surviving resistant bacteria reproduces asexually (divides by mitosis) to form identical clones passing resistant genes to their offspring. A population of antibiotic resistant bacteria is produced. If this continues to happen the bacteria could develop multidrug resistance to many antibiotics.
129
Which bacteria shows multidrug resistance?
MRSA which is resistance against penicillin and all its derivatives
130
What do bacteria become?
Resistant not immune
131
How has antibiotic resistance occurred?
Bacteria is now capable of surviving exposure to the antibiotics and bacteria divide rapidly and optimum conditions and have a high mutation rate.
Resistance occurs due to random genetic mutations in the bacteria population.
The overuse of antibiotics
Naturally occurring mutations that confer resistance to antibiotics have given these bacteria a selective advantage in the presence of antibiotics.
132
What has the overuse of antibiotics resulted in?
Accidental selection of bacterial strains that are now completely unaffected by some antibiotics.
133
How is antibiotic resistance likely to develop?
If they are prescribed for trivial infections (antibiotics tend not to be given food poisoning)
People do not complete a prescribed course of antibiotics (important in treating TB)
Routinely used in intensive farming.
134
How is antibiotics described as?
The selection agent
135
Describe natural selection in terms of antibiotic resistance?
All these would cause low levels of antibiotic resistance genes. Low levels of antibiotics will be present in the environment which would kill the most susceptible bacteria leaving stronger ones to multiply and gradually produce resistant strains.
136
What is TB caused by?
By the bacillus bacteria Mycobacterium tuberculosis which is gram-positive is chained.
137
Describe the structure of the TB bacteria?
It has a waxy coat covering the cell wall which means it can resist dehydration so can survive in dust.
Prokaryotic= no nucleus or membrane bound organelles
Rod shaped= bacillus
Peptidoglycan cell wall (some lipid)
Circular DNA in a double helix with no histone proteins
Plasmids
138
What is TB named after?
The tubercles or nodules of dead or damaged cells in the lungs of infected people. Tubercles may contain gas filled cavities which are visible on X-rays.
139
How do you know TB is gram-positive?
Due to the staining causing it to turn a purple colour. It's difficult to kill due to the fact it has a lot of lipid mix into its cell wall (60%)
140
Is TB easily transmitted?
The infection spreads rapidly by aerosol transmission i.e. the inhalation of bacteria laden droplets from coughs and sneezes of infected people. It spreads rapidly in overcrowded conditions. HIV and AIDS sufferers have a weakend immune system with TB rates increasing partially due to the link with HIV epidemic.
141
Where does the TB bacterium mainly affect?
It made me affects the lungs and the neck lymph nodes. If the lungs are affected the patient can develop chest pains and can cough up phlegm which contains blood. The lymph nodes can swell and people can lose their appetite and develop a fever. In 15 to 20% of active cases the infection outside the lungs can cause are the types of TB.
142
What are the TB symptoms?
```
Coughing
chest pain
coughing up blood
high fever
profuse sweating
shaking chills (range from moderate to severe) headache
```
143
How is TB treated?
```
A long course of antibiotics but M. tuberculosis does show antibiotic resistance.
Two antibiotics (isoniazid and rifampicin) for 6months to 1 year
Two antibiotics (pyrazinamide and ethambutol) for the first 2 months.
```
144
How is TB prevented?
By the BCG vaccine (Bacillus of calmette and Geurin) which is given to babies and if a skin test proves negative to people up to 16. It provides 75% protection for five years. The vaccine is made from attenuated strain of a related bacterium M. Bovis which is freeze dried. It is effective against TB meningitis. Its only give to children in high risk areas.
145
What is the heaf test?
It's purified protein extracted from TB bacteria is infected and the skin with a six pointed needle it is red after 2 to 3 days. If it causes redness or swelling at the site of injection it indicates a positive reaction.
146
How else is TB prevented other than the vaccine?
Better, less cramped, more hygienic living conditions
Eradicating poverty
Health checks at Ports
X-ray screening for detection
Quarantine for infected patients
Checking for TB and drinking pasteurised milk.
147
How does TB progress in the body?
1. Bacteria enters the lungs.
2. Macrophages engulf them.
3. The bacteria survive inside the macrophages that triggers other cells to produce histamine (inflammatory response).
4. Other white blood cells move to the infected area and form a mass of tissue surrounded by fibres and lymphocytes outer layer called a granuloma (or tubercle)
148
How is active TB caused?
If someone has a compromised immune system due to: Malnutrition, HIV, Immunosuppressant drugs, Age. The bacteria can escape the granuloma and cause active pulmonary TB.
149
What are the favoured conditions for the transmission of TB?
Cramped living conditions – bacteria can spread easily Poor healthcare – disease is undetected and untreated Poverty – can't afford healthcare
HIV/AIDS – immune system unable to destroy bacteria.
150
How does drug resistant TB occur?
If a patient fails to take their full (6 to 12 months) course of medication necessary to destroy all and tuberculosis present. If patients are treated with too few OR inadequate doses. A lack of compliance is that patient may feel better after the first 2 to 4 weeks and stop taking the medication. Multidrug resistant TB is caused by and tuberculosis strands resistant to 2 or more drugs.
DOTS – Directly Observed Therapy Short-course is when patients are given a short course of antibiotics whilst observed by a healthcare worker which increases completion of the course and reduces risk of antibiotic resistance.
151
What is cholera caused by?
It's caused by a gram negative bacteria called the vibrio cholerae. It is a serious and often fatal disease of the human and is an endemic in much of the world. The bacterium is, shaped with a flagellum which allows them to move through water. It can only reproduce once inside its human host
152
Tell me about the vibrio cholerae?
It lives and multiplies in the small intestine. It produces a powerful endotoxin which caused violent information of the mucus membrane of the gut. Many pathogens are required to closest to disease as your stomach acid can kill them. It lives in water and food and affects people through contaminated sources.
153
What do humans act as with cholera?
They act as reservoirs or carriers and contaminate water supplies in which the organism is transmitted.
154
What are the symptoms of cholera?
The main symptom is copious amounts of diarrhoea due to an irritation of the bowel by the end of toxin produced by the vibrio bacteria. The typical case produces 10 to 20 L of watery diarrhoea with 1000 vibrios in 1 mL of diarrhoea so it is easily spread. It also causes vomiting and muscle cramps.
155
Why does someone die from Cholera?
Due to dehydration and loss of mineral salts this is from the copious amount of diarrhoea.
156
How is cholera transmitted?
Drinking contaminated water by faeces containing organisms. Contaminated food. Direct contact between person to person (rare).
157
Why is cholera common in developing countries?
Due to lack of sanitation systems. People rely on collecting water from local sources like to visit lakes as there are no tax on houses. Water can be contaminated with faeces during heavy rain and flood water overwhelms pit toilets when they over flow and run into water sources.
158
What is meant by asymptomatic carriers?
It's when people can carry the bacteria in the intestine without developing symptoms. There are a few of vibrios in the gut of the carriers but still poses a threat to public health England. Some people stop defecating vibrios after a week.
159
Why do breastfed children not catch cholera?
As they aren't eating or drinking from contaminated sources
160
Describe the distribution of cholera?
It was an endemic in the UK in Europe but due to sanitation improvement the disease has disappeared.
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How is cholera treated?
Treat dehydration by rehydration of salt i.e. salt, glucose and non-contaminated fluids. It can be taken orally or intravenously.
Drug Treatment – antibacterial drugs like tetracyclines shorten the period of diarrhoea and excretion of vibrios. It reduces fluid requirements of the patient. But are expensive and can be inaccessible for some areas and that can lead to antibiotic resistance if overused.
A vaccine is given as a supporting measure instead of a control as only prevents 40 to 80% of people from Dell developing cholera with protection being temporarily (3 to 6 months).
162
What are the public health measures for cholera?
An outbreak must be detected early
A bacterial culture grown quickly to diagnose the vibrios
Rapid treatment and isolation from community Education in: food hygiene, hand washing after defecating, dangers of contaminated water and methods of disinfection of water.
Better sewage treatment
Good hygiene
Sanitation
Better water treatment
163
Describe the mechanism of water loss in epithelial cells due to cholera?
Vibrio cholera bacteria nestles in the nucleus lining of the epithelium. A toxins produce which attaches to the carbohydrate receptors on the epithelial cell membrane (gangliosides receptors) activating the opening of the chloride ion channels in the membrane. Chloride ions move from the cell into the lumen and sodium ions flow. Other ions e.g. potassium ions and hydrogen carbonate ions diffuse from the cell to the lumen. Water flows down the water potential gradient from the bloodstream of the the cell into the lumen by osmosis resulting in a very watery diarrhoea, loss of salt and dehydration.
164
Why are there three different subgroups of the influenza flu and what are they based on?
They all have different antigenic types (drained) but all come from the same virus. The three groups are A, B and C which are based on their core proteins.
165
What is influenza A?
It's the most common and infects humans as well as birds, pigs and other animals but it's not transmitted from human to human.
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What is influenza B?
This virus causes the same spectrum of disease as influenza A
167
What is influenza C?
It causes a mild upper respiratory tract illness, lower respiratory tract complications are rare. There is no vaccine for influenza C
168
How do pandemics occur?
With each group there are many different antigenic types when a new strain develops and appears with new proteins on the virus surface the human immune system is not able to provide adequate protection as a result of lack of immunity.
169
Describe the structure of the influenza virus?
It contains RNA as its genetic material with the RNA having 8 single strands instead of one which is unusual. The virion is surrounded by phospholipid envelope derived from the hosts cell surface membrane. Envelope contains two important proteins which are antigens and there's spikes on the surface of the virus particle.
Haemagglutinin (H) has a role of entering the hosts cell
Neuraminidase (N) has a role of leaving the hosts cell.
E.g H1N1 (swine flu) and H5N1 (bird flu)
Transmitted to humans from pigs/birds. Its not usually passed from human to human but did in 2009
170
How is the influenza virus transmitted?
As the spread is not easily controlled it spreads rapidly from person to person by droplet infection from coughs and sneezes and aerosol transmission. The droplets are initially 10-100 micrometres diameter but dry rapidly to a droplet nuclei of 1-4 micro meters containing virus particles. The mucus protects the virus. It survives better when the air is dry and low UV light (survives better in winter than summer).
171
What does the influenza virus infect?
If infects the lining of the upper respiratory tract which generate aerosols. The virus attacks mucous membranes especially in the upper respiratory tract. It destroys the respiratory epithelium.
172
What are the symptoms of influenza?
```
Sore throat
coughing
fever
sudden headaches
chills
appetite loss
muscle aches
tiredness secondary
bacterial infections - treated with antibiotics to relieve symptoms but won't cure the viral infection
```
173
Describe the pandemics caused by influenza?
It killed an estimate of 20–50 million people in the
1918–1919 pandemic with the H1 N1 strain being responsible the strain had genes of the avian (bird) origin.
In 1957 a pandemic of Asian flu (H2N2) killed 2 million
In 1968 the Hong Kong Flue killed 1 million
174
How is influenza treated?
How do people recover with rest and fluids however some may require hospital treatment if they become critically ill.
Anti-viral drugs (given if you are particularly susceptible) target the virus directly however in most cases they aren't given.
The drugs prevent: Attachment/ entry into the host cell
Nucleic acid replication
Virus Protein processing
Virus maturation
175
How is influenza prevented?
Regular hand washing
Using and discarding tissues after use
Quarantine
Vaccination programmes.
176
Describe the vaccination programme for the influenza virus?
Annual vaccines are given to the elderly and people at risk of respiratory infections e.g. asthmatics and pregnant women post. Each year the vaccine contains most common types in the year before. It's 70–80% effective but not 100% due to the emergence of new strains. The surface antigens can change to a new vaccine is needed annually.
177
Why can you get infected with influenza two years in a row?
As it's constantly mutating you produce memory cells of one strain of flu but you can still develop the disease if you're infected by a different strain as your memory B cells won't recognise it and you won't have immunity from the first infection.
178
What is antigenic drift?
There is no RNA proofreading enzymes so following each round of replication on average every new virion has a new mutation. It produces a gradual change in surface proteins – antigenic drift. Which is why a vaccine is needed each year.
It causes a constant change.
179
What is antigenic shift?
It's when a genetic reassortment can occur. Flu A has 16 different types of haemogglutinin of which H1, H2, H3 are the most common in humans. It has 9 different types of neuraminidase of which N1, N2 are the most common in humans. If one cell if infected by viruses that have a different combination of H and N e.g H1N1, H2N1 the separate strands of RNA can recombine to give rise to e.g H1N1 and N2N2.
Antigenic shift causes epidemics
180
What is the animal reservoir in new infections in humans?
Chickens and pigs
181
What is smallpox caused by?
A DNA causing virus, variola major
182
Explain the history of smallpox?
It killed 500 million between 1900 to 1979. With a 30–60% fatality rate. In 1980 it was declared eradicated following vaccination campaigns. It's the only organism that humans have intentionally made extinct (outside specialist labs). Ethical labs debate on its extinction.
183
How is smallpox transmitted?
It is inhaled or transmitted via saliva or from of the bodies if they are in close contact with an infected person. It enters small blood vessels in the skin, mouth and throat throat and is dispersed around the body. It is highly infectious.
184
What are the symptoms of smallpox?
Arash followed by fluid filled blisters which cause scars.
| Scars on the cornea results in blindness and some survivors have a limb deformities.
185
What is the treatment for smallpox?
Infected people are given fluids and drugs to control the fever and pain. Antibiotics may be given to control any secondary bacterial infections.
186
How was smallpox prevented?
A vaccine produced a strong a new response which was made with live vaccinia the virus (the first life vaccine) across smallpox relative was very effective against a disease.
187
Why was the small pox vaccine a success?
Low mutation rates /Antigenic variation and highly immunogenic nature of its component antigens.
No animal reservoir
The programme was simple and people were keen to get it after seeing the affects it had on people.
It was cheap to produce and was made with a similar virus. It can be freeze dried and kept at high temperatures.
188
What is malaria?
It is a serious and often fatal disease which is an endemic in some subtropical areas. Plasmodium is transmitted by over 100 species of anopheles mosquitoes when they pierce the skin to take a blood smell. The females are vectors of malaria and the males aren't as they feed off plant nectar not blood. It occurs in habitats that supports anopheles mosquito.
189
What is malaria caused by?
Plasmodium a Protoctistan parasite
190
What are the four species of plasmodium that cause a disease in humans?
Plasmodium falciparum (causes most deaths)
Plasmodium vivax (major killer)
Plasmodium ovale
Plasmodium malarae
191
What is the global distribution of malaria?
Because in over 100 tropical countries where the vector can survive for more than 40% of people in the world are at risk.
192
How is malaria transmitted?
The parasite hides inside body cells so that the immune system is unable to detect and fight it.
The organism initially invades the liver cells and then multiplies in red blood cells which burst releasing more parasites and causing severe bouts of fever.
193
Describe the lifestyle of mosquito and malaria?
When a mosquito takes blood from infected person it takes place in the sexually producing stage of the plasmodium gametocytes. Which produce zygote which develop into an infective stage called sporozoites. Sporozoites migrate from mosquitoes gut to salivary glands.
When they take another meal, the sporozoites in the mosquito saliva is infected into the human. Which travel to the liver and reproduce asexually in the liver cells producing merozoites.
These are released into the blood and infect red blood cells where they do more asexual reproduction.
The red blood cells burst and release more merozoites which affect more red blood cells.
This cycle repeats every few days when the blood cells burst the favour returns.
Some merozoites become gametocytes.
194
What is treatment for malaria?
Drug treatment is available but may need to reduce the chance of infection. They should be taken before, during and after a trip where malaria is an endemic. Plasmodium is it affected by drugs went outside but cells but these have limited effectiveness and side-effects with resistance increasing.
Chloroquine (contains quinine) is the most commonly used antimalarial drug in Africa which reduces the number of parasites in the body but resistance is rising steadily.
195
What does quinine do?
It interferes with the growth and reproduction of plasmodium and attacks the parasites once inside the red blood cells. It kills a parasite and prevent them from multiplying further however it's not fully understood how it kills them.
196
What is arthemether?
It's a fast effective drug which is more expensive against battling malaria
197
What does artemisinin do?
It kills plasmodium at the erythrocytic phase (when mirrors lights have infected red blood cells). The drug comes into contact with the Haem group of haemoglobin to release radicals which killed plasmodium. It has a low toxicity to humans
198
Why is there no vaccine for malaria?
P. Falciparium mutates frequently and produces many antigenic types so it's not possible to produce a vaccine.
There are many stages in the parasites life-cycle with different antigens.
The parasite hide from the new system.
Antibodies are only effective when outside body cells so limiting the target stages for a vaccine.
199
How is malaria prevented?
By the knowledge of the life-cycle of the vector and the parasite in order to exploit it weak points.
200
How is malaria controlled?
Sleep under nets – mosquitoes feed between dusk and dawn so prevents being bitten.
Nets are treated with pyrethroid insecticide – kills mosquitoes.
Spray walls with insecticide – kills mosquitoes as they rest on walls after feeding.
Wear protective long sleeves and trousers.
Drown or cover stagnant water e.g. water tanks, pond – removes mosquitoes access to egg laying/breeding sites.
Film of oil on the water – lowered water tension prevents larvae obtaining piercing the surface to obtain oxygen (stops the larvae from breathing).
Fish introduced into water – Larvae are aquatic so fish eat them.
Spray water with insecticide such as synthetic pyrenoids.
Spray water with pathogenic bacteria to kill larvae. Infecting mosquitoes with bacterium wolbactia – this blocks the development of plasmodium.
Male mosquitoes are sterilised with x- rays after they mate so no offspring is produced.
201
Describe the structure of a virus?
They are very small.
Surface proteins – the spikes allow the virus to attach to receptors on the target cell.
Viral envelope – a piece of plasma membrane budget or from the last human host cell.
Nucleic acid – two identical strands of RNA which contains a genetic blueprint for making more viruses. Reverse transcriptase –two copies of the important enzyme to transcribe RNA into DNA once inside the host.
Capsid – protein coat that protects the nucleic acid
(rRNA) within.
They only reproduce once in a high cell.
202
What happens in the lytic cycle?
Viruses immediately reproduce once inside using the hosts metabolism to copy their own nucleic acid and synthesise a new protein coat.
Lysis of the host cell e.g. common cold virus.
Budding which they acquire an envelope from the house of membrane e.g. influenza virus.
203
What happens at the lysogenic pathway?
It's when the virus converts its RNA to DNA using reverse transcriptase which then inserts into the hosts genome where can remain there for many generations with no clinical effect. They enter the lytic cycle at some point in which symptoms occur e.g. HIV, herpes Symplex, chickenpox.
204
How do viruses cause cell lysis?
When bacteria infected with bacteriophage the pressure inside the new virus particle causes the bacteria to burst. In virus-infected animal cells inflammation caused by T-lymphocyte causes lysis (as well as antibodies)
e.g. rhinovirus causes a common cold which lysis cells in the upper respiratory tract. This virus may cause death of the host cell. Breaking a cell apart as the virus particles leave the infected cells could be destroyed by Killer T cells and remain engulfed by phagocytes.
205
How does viruses trigger cells to be cancerous?
HPV(human papilloma virus) infects epithelial cells in the cervix which causes cancer by activating
pro-oncogenes or deactivating tumour suppressor genes.
All girls are offered the HPV vaccine to prevent infection at 9-13 with cervical smears every 3–5 years for ages 25–64.
206
How does a virus suppress the immune system?
HIV affects T-helper cells which are destroyed and decrease in number which suppresses the immune system so people with AIDS are likely to catch opportunitistic infections like TB
207
What do some toxins cause from viruses?
Many viral components and their byproducts are toxic. Measles virus can cause chromosome fission.
Herpes virus can cause cell fusion.
Viral proteins inhibit RNA, DNA and protein synthesis.
208
What happens if bacterial cells are infected with viruses (bacteriophage)?
They lyse due to the phage enzyme lysozyme and intracellular pressure of the virus.
