4.6 Immunology & Disease Flashcards
(72 cards)
1
Q
Define pathogenic
A
An organism that causes damage to its host
2
Q
Define infectious
A
A disease that may be transmitted from one individual to another
3
Q
Define a carrier
A
- shows no symptoms when infected
- can pass disease onto another
4
Q
Define a disease reservoir
A
- where a pathogen is normally found
—> animals or humans, and could be a source of infection
5
Q
Define an endemic
A
A disease which is always present at low levels in an area
6
Q
Define fomities
A
- objects or materials that are likely to carry infection
—> clothes, utensils and furniture
7
Q
Define an epidemic
A
Where there is a significant increase in the usual number of cases of a disease, associated with rapid spread
8
Q
Define a pandemic
A
- epidemic occurring worldwide or over a very wide area, crossing international boundaries
- affects a large number of people
9
Q
Define a vaccine
A
- uses non-pathogenic forms, products or antigens of microorganisms to stimulate an immune response
- gives protection against subsequent infection
10
Q
Define antibiotics
A
- substances produced by microorganisms that affect the growth of other microorganisms
11
Q
Define antibiotic resistance
A
- where a microorganism that should be affected by an antibiotic is no longer susceptible to it
12
Q
Define a vector
A
A living organism that transfers a disease from one individual to another
13
Q
Define a toxin
A
A chemical produced by a microorganism which causes damage to its host
14
Q
Define antigenic types
A
- organisms with similar or the same antigens
- subgroups or strains of microbial species which may be used to trace infections
—> identified by antibodies
15
Q
What are the origins of cholera?
A
- caused by gram negative bacteria
- only reproduce when inside human host
- endemic in parts of the world - people infected by contaminated food or water and become carriers that can contaminate other water supplies
16
Q
How does cholera impact the body?
A
- toxin produced by the bacteria inside the small intestine impacts the chloride channel proteins called CFTR
- water and many ions are not absorbed into blood so patient has severe, watery diarrhoea which causes dehydration and dramatic loss of blood pressure
17
Q
What are the methods to improve/treat cholera?
A
- prevented with good hygiene and sanitation
- a vaccine with either genetically engineered or inactive bacteria is an option to give temporary protection
- treatment once contracted can either be giving patients electrolytes, or bacteria treated with antibiotics
18
Q
Describe the cause and spread of TB
A
- bacillus bacterium
- named for the dead and damaged cells in lungs of those infected
- spreads by aerosol transmission especially in crowded conditions
- seen a lot in HIV/AIDS patients since they have decreased immune system
19
Q
Impact of TB
A
- affects lungs so patients develop chest pain and cough up blood
- bacteria may infect lymph nodes and give fever like symptoms
20
Q
Treatment for TB
A
- long course of antibiotics
- BCG vaccine given to babies
21
Q
Cause and impact of small pox
A
- caused by a DNA containing virus
- virus inhaled or transmitted in saliva
- enters small blood vessels in the skin, mouth and throat
- causes a rash and fluid filled blisters which leave scars
- some suffer blindness and limb deformities
22
Q
Treatment for small pox
A
- fluids and drugs to control fever and pain
- antibiotics given to control secondary infection
- smallpox vaccine provides strong immune response and is very effective at preventing disease
- it is the only species humans have made deliberately extinct
23
Q
Describe the origins of influenza
A
- many sub groups that affect many species
- new strain appears with new proteins on the virus surface, the immune system cannot provide protection which results in pandemics
- contains RNA as genetic material
24
Q
Describe the structure of the influenza virus
A
- RNA in 8 strands
- virion surrounded by phospholipid envelope derived from the host cells surface membrane
- envelope contains 2 types of antigen;
—> haematglutinin (HA) has a role in entering host cell
—> neuraminidase (NA) has a role in leaving cell
25
How does the flu impact the body?
- attacks mucous membranes in upper respiratory tract, causing sore throat, cough and fever
26
Ways to reduce risk of flu infection
- hand washing
- binning used tissues
- annual vaccine
- quarantine
- antibiotics to prevent or treat secondary infections
27
What is meant by an antigenic type?
- different individuals of the same pathogenic species with different surface proteins, generating different antibodies
28
Describe antigenic drift
- no RNA proofreading enzymes so following each round of replication, each virion has a new mutation
- produces a gradual change in surface proteins
- particularly impacts HA which is why new vaccine needed annually
29
Describe antigenic shift
- different combos of NA and HA lead to diff virus types
- cause epidemics
30
Describe the origins of malaria
- caused by protoctistan Plasmodium
- transmitted by over 100 species of Anopheles mosquitos when they pierce skin to drink blood
- females are vectors but males are not
- occurs in habitats that support the Anopheles mosquitos
—> endemic in sub tropical regions, can be epidemic in wet seasons and regarded as pandemic
31
Describe the transmission of malaria
- when a mosquito takes blood it takes in the sexually reproducing stage of Plasmodium called gametocytes
- they produce zygotes which develop into an infective stage called sporozites
- sporozites migrate from the mosquito’s gut to its salivary glands
- when mosquito takes another feed, the sporozites are injected into the human and then travel to the liver and reproduce asexually, producing merozites
- merozites released into blood and infect red blood cells
- red blood cells burst and release more merozites released into - process repeats many times
- some merozites become gametes
32
Describe the treatment of malaria
- drugs do not attack Plasmodium when it’s inside cells so effectiveness is limited
—> use artemisinin and combo of other drugs as unlikely to be resistant to them all at the same time
- unable to produce vaccine due to variety of antigenic types and mutations
33
Describe preventative measures for malaria based in mosquito behaviour
- sleep under nets
- pyrethroid insecticide on nets
- spray indoor walls with insecticide
- drain or cover stagnant water
- film of oil on water
34
Describe preventative measures for malaria - biological control
- fish introduced to water to eat larvae
- infect mosquitos w bacteria which blocks plasmodium development
- sterilise male mosquitos with x-rays - no offspring
35
Methods of viral release
- lysis of a host cell
- budding (acquire an envelope from host cells membrane)
36
What is meant by a lysogenic virus?
- integrate nucleic acid into host cell genome and may remain in there for many cell generations with no impact
- enter the lytic cycle at a later time which is when they produce symptoms
37
Describe the virus life cycle
- virion attaches to cell
- viral nucleic acid is injected into the cell, leaving the protein coat outside
- nucleic acid and capsid protein are synthesised using the hosts metabolism and they assemble to make mature virus particles
- cell lysis releases viruses or new virus particles bud off of the cell surface
- viral nucleic acid integrates into the host cell chromosome
38
Describe viral pathogenicity via cell lysis
- when bacteria are infected by bacteriophage, the pressure of viral particles causes bacteria to burst
- in infected animal cells, lysis is caused by T-lymphocytes or antibodies
39
Describe viral pathogenicity via toxins
- viral components and by-products are often toxic
- viral proteins can inhibit RNA, DNA and protein synthesis
40
Describe viral pathogenicity via cell transformation
- viral DNA can integrate into host chromosome
- if the DNA inserts a proto-oncogene or tumour suppressing gene it can result in rapid and uncontrolled cell division (cancer)
41
Describe viral pathogenicity via immune suppression
- suppression of reactions that cause B and T lymphocytes to mature
- reduction of antibody formation
- reduction of phagocytic cells engulfing microbes
42
State the antimicrobial types
- antiseptics used on living tissue
- disinfectants used on non-living surfaces
- antibiotics
43
Differentiate between board spectrum and narrow spectrum antibiotics
- broad spectrum affect many gram +ve and gram -ve species
- narrow spectrum are selective in the bacteria they affect
44
Differentiate between bactericidal and bacteriostatic antibiotics
- bacteriacidcal kill bacteria
- bacteriostatic prevent bacterial multiplication but do not cause death (bacteria resume normal activity when antibiotics aren’t present)
45
Describe the peptidoglycan cell wall
- polysaccharide and short amino acids
- transpetidase enzymes cross link the polysaccharide molecules by attaching them to amino acids
- cross-linking makes cell wall strong, gives it shape and prevent osmotic lysis
46
Describe the mechanism of penicillin
- penicillin readily diffuses into the cell wall of gram +ve bacteria and enters some gram -ve bacteria through porins which form pores in the LPS layer
- enzyme DD-transpeptidase catalyses the condensation reactions that make cross links between AA and PD molecules
—> penicillin binds to the protein and acts as an enzyme inhibitor
- breakdown by hydrolysis occurs and more cell wall is lost than gained
- no peptide cross links are made so precursor molecules build up and are also hydrolysed
- cell wall is weakened so that as water enters the cell by osmosis, the wall is too weak to withstand the increase pressure potential so the cell lyses
47
Describe the mechanisms of tetracycline
- broad spectrum antibiotic
- inhibits protein synthesis
- diffuses and is pumped into bacteria cells
- binds to the small subunit of ribosomes and blocked tRNA attachment in the second position so no new amino acids can be added to a polypeptide chain
- binds reversibly so it is bacteriostatic
48
Describe the sources of antibiotic resistance alleles
- bacteria divide rapidly therefore have a high mutation rate
- bacteria may acquire plasmids that carry an allele for resistance - plasmids replicate inside the bacterium and are passed onto the daughter cells when the bacteria replicate
49
Describe ways in which bacteria can be resistant to penicillin
- secrete an enzyme that degrades penicillin
- altered PBP so penicillin cannot bind
- reduce penicillin entry with fewer or smaller porins
50
Describe ways in which bacteria can be resistant to tetracycline
- pumps tetracycline out of cell
- dislodge bound tetracycline
- prevent tetracycline attaching to a ribosome
51
Why does continuous high levels of antibiotics lead to resistance?
- resistant bacteria only have a selective advantage when antibiotics are present
- selective advantage leads to increased allele frequency
- if no antibiotics, then those bacteria will have a selective disadvantage and die
52
Describe ways in which the innate immune system resists infection
- skin covers bodily surfaces - keratin makes skin waterproof, collagen makes skin tough
- flora outcompete pathogenic strains
- microorganisms trapped by mucus
- blood clots prevent entry of microbes and inflammation brings large numbers of phagocytic cells and increase temperature to prevent microbial growth
- microbes in blood stream engulfed by phagocytic cells
- tears, mucus and saliva contain lysozyme which hydrolyses the peptidoglycan molecules in bacterial cell walls
- stomach acid kills many of the microbes ingested in food and drink
53
What provides the adaptive immune response?
Lymphocytes
54
Describe the humoral response (stage of the adaptive immune response)
- results in antibody production
- B lymphocytes mature in the spleen and lymph nodes and the receptors on their cell membranes respond to a foreign protein and divide to produce plasma cells (release antibodies) and memory cells (remain dormant if same antigen is encountered)
55
Describe antibody structure
- Y-shaped glycoprotein molecules called immunoglobulins
- quaternary structure as each molecule made of 4 polypeptides held by disulphide bonds
56
Describe the cell mediated response (stage of the adaptive immune response)
- activation of phagocytic cells (B and T lymphocytes)
- T lymphocytes are activated in the thymus gland, and receptors on membrane divide to make:
—> T memory cells
—> T killer or cytotoxic T cells
—> T helper cells which release cytokines
57
Role of cytokines
- balance the humoral and cell-mediated responses by stimulating:
—> phagocytic cells which engulf and digest pathogens
—> B and T lymphocytes to undergo clonal expansion
—> B lymphocytes to make antibodies
58
Describe the primary immune response
- on first exposure to an antigen, there is a latent period in which macrophages engulf the foreign antigen and incorporate the antigenic molecules into their own cell membranes
—> antigen presentation
- T helper cells detect these antigens and respond by secreting cytokines
- B plasma cells secrete antibodies for about 3 weeks, and symptoms of infection subside
59
Describe the secondary immune response
- relies on memory cells to protect against an identical antigen
- on re-exposure memory cells undergo clonal expansion but much faster than the primary response
- remain at high conc in circulation for longer and no symptoms develop
60
What can be used as vaccines?
- antigens isolated from the pathogen
- mRNA (synthesised if pathogens base sequence is known, translated by the body into the pathogens proteins ie antigens)
- weakened or attenuated strains of the pathogen
- inactive or killed pathogen
- inactivated toxins
61
Why are booster vaccines given?
- number of memory cells decreases over time
- further exposure to the vaccine to give a longer, faster and quicker response
62
What is passive immunity and what are some ways it can happen?
- body receives antibodies produced by another individual
- transferred from mother to foetus across placenta
- transferred to the baby in breast milk
63
Why might antibody injections be used?
- when rapid resistance is needed and there is no time for the active immune response to develop (ie bitten by a rabies infected animal)
- cases of primary immune deficiency disease and cases of acquired immunity conditions where patients don’t make enough antibodies
64
What is required for a vaccine to protect successfully against a disease?
- antigen should be highly immunogenic
—> single dose will provide a strong immune response
—> rapidly make a large number of antibody molecules
- only one antigenic type of the pathogen
65
What is meant by herd immunity?
- when enough people are vaccinated against a disease, there are fewer pathogens in the population so fewer people will get infected
66
Why might people not be vaccinated?
- immunocompromised, chemo, HIV/AIDS, very old or very ill
- religious objections, safety fears, preference for natural medicine, mistrust of pharmaceutical companies
67
What is a T helper cell?
A type of T lymphocyte that regulates the immune response through the release of cytokines
68
What is a T killer cell?
A type of T lymphocyte that causes lysis of damaged or infected cells
69
Why are viruses difficult to treat with drugs?
- viruses ar ento cellular so don’t have metabolic pathways
- drugs would need to interfere with hosts metabolism after virus has integrated
- if vaccine were developed it would need to target the virus before it enters cells
70
Suggest how erythromycin may work to treat bacterial infection and why it does not affect the patients cell metabolism
- inhibits protein synthesis
- humans have different ribosomes to bacteria
71
72
Explain how agglutination tests can be used to distinguish between strains of bacteria
- antibodies are specific to an antigen
- different strains have different antigens
- if no agglutination occurs then there are different strains
