The Immune System Flashcards
(118 cards)
1
Q
What is the immune system designed to do?
A
defend the body against disease-causing organisms (PATHOGENS), some toxins (POISONS) produced by living things and cancer cells.
2
Q
What is immunity?
A
the ability of the body to resist infection OR to destroy the pathogen if it succeeds invading.
3
Q
What are the three lines of defence and state whether they are specific or non-specific?
A
First - non-specific
Second - non-specific
Third - specific
4
Q
What are the main mechanisms of the first line of defence?
A
Physical barriers e.g. skin
Chemical barriers e.g. mucus, acid, lysozymes in tears & saliva)
5
Q
What are the main mechanisms of the second line of defence?
A
Inflammatory response
Phagocytosis
Natural killer cells
6
Q
What are the main mechanisms of the third line of defence?
A
T lymphocytes ( from thymus) B lymphocytes (from bone marrow)
7
Q
What does non-specific immunity mean?
A
the immune system will work against ANY type of disease-causing agent
8
Q
What do physical barriers do?
A
prevent the ENTRY of pathogens.
9
Q
As a physical barrier, what does the skin do?
A
skin surface is composed of epithelial cells to provide physical protection against bacteria and viruses
10
Q
What are mucous membranes?
A
linings of digestive and respiratory tracts are composed of epithelial cells forming another physical barrier
11
Q
What are lysozymes?
A
secretions from tears and saliva containing the enzyme lysozyme which digests bacterial cell walls
12
Q
What do secretions from sweat and sebaceous glands do?
A
these keep skin at a pH too low for microbes to thrive
13
Q
What does acid do?
A
hydrochloric acid is secreted by the lining of the stomach to destroy many ingested pathogens
14
Q
What are the 3 second lines of defence?
A
inflammatory response
phagocytosis
natural killer cells
15
Q
Describe the inflammatory response?
A
This is a localised defence mechanism at an affected site. Mast cells are present in connective tissue. They release a substance called histamine which causes vasodilation of local capillaries, causing them to become swollen with blood. The area then becomes red and inflamed. Histamine also makes the capillary walls become more permeable so more fluid leaks out into the surrounding tissue, causing them to swell.
16
Q
What is also produced during the inflammatory response and what is their job?
A
Cytokines are produced. They are cell-signalling proteins secreted by many cells, including white blood cells. Their job is to stimulate the movement of phagocytes towards an injury site and accelerate the delivery of antimicrobial proteins and blood-clotting chemicals to an injury site.
17
Q
What are the cells able to undergo phagocytosis and what do they do?
A
phagocytes, a specialised type of white blood cell. They detect a chemical released by bacteria and move up a concentration gradient towards it. They then engulf the pathogen and digest it using digestive enzymes (usually a combination of lysozymes, proteases and nucleases) contained in a vesicle inside them.
18
Q
Describe in detail the stages of phagocytosis?
A
- Microbe adheres to phagocyte
- Phagocyte forms pseudopods that eventually engulf the pathogen. (endocytosis)
- Phagocytic vesicle forms cotaining pathogen and then fuses with a lysosome.
- Microbe in fused vesicle is killed and digested by lysosomal enzymes within the phagolysosome, leaving a residual body.
- Indigestible and residual material is removed by exocytosis.
19
Q
What does the phagocyte release following the digestion of the microorgainisms?
A
cytokines which attract more phagocytes to the infected area.
20
Q
When dead bacteria and phagocytes accumulate at an infected site what do they form?
A
pus
21
Q
What are natural killer cells?
A
Another type of white blood cell that constantly roam the body in the bloodstream looking for signs of an infection. They can also release cytokines but mainly play an important role in destroying pathogen-infected cells (usually by a virus) or cancer cells.
22
Q
What do natural killer cells do (describe stages)?
A
- Once a target cell is identified, the Natural killer cell releases a protein which forms a pore through the target cell’s membrane.
- Signal molecules from the NK cell enter via the pore and switch on a suicide gene in the DNA.
- The suicide gene switches on the production of self-destructive enzymes ultimately causing the cell to shrink and die (called APOPTOSIS).
23
Q
What is meant by specific immunity?
A
the immune system works against a particular pathogen
24
Q
What are the 2 types of lymphocytes (T or B) created from?
A
stem cells in the bone marrow
25
Describe the formation of B lymphocytes?
B lymphocytes are created in the bone marrow where they mature before being released into the bloodstream.
26
Describe the formation of T lymphocytes?
T lymphocytes are also created in the bone marrow but travel to the thymus gland to mature before being released into the bloodstream.
27
What does using lymphocytes to attack specific pathogens involve? (5)
1. Recognition of self/non-self
2. Immune surveillance
3. Clonal selection theory
4. Action of B & T lymphocytes
5. Immunological memory
28
What do antigens allow?
our immune system to recognise our own cells (self)
29
What is meant by antigen signature?
each person has their own unique (genetically determined) combination of antigens
30
What do B and T lymphocytes have on their cell membranes?
receptors that can combine with antigens on other cells
31
What happens during B and T lymphocyte maturation?
any lymphocyte that bears an antigen receptor that would fit the body's own antigens are weeded out and destroyed by apoptosis.
32
What do invading bacteria and viruses have on their cell membranes?
different antigens which are foreign to us (non-self)
33
What happens if a virus invades a cell?
that cell can become an antigen-presenting cell
34
Following phagocytosis, what can phagocytes become?
antigen-presenting cells
35
What is immune surveillance?
A range of different white blood cells roam the circulatory system continuously monitoring the tissues for signs of damage or invasion by pathogens.
36
What can white blood cells do during immune surveillance?
squeeze out through tiny spaces in the walls of capillaries to gain access to surrounding tissues. If damage/ invasion is detected, some white blood cells release cytokines into the blood. These attract phagocytes and T lymphocytes to the site.
37
Describe the clonal selection theory?
Each person's body possesses a pool of lymphocytes, each bearing a specific type of antigen receptor. If one of these lymphocytes finds its complementary non-self antigen-bearing cell, it activates it to divide repeatedly, forming a clonal population of identical lymphocytes, all bearing the same receptor.
38
What do T cells account for?
more than 80% of circulating lymphocytes
39
What are the 2 main groups of T lymphocytes?
Helper T cells
| Cytotoxic T cells
40
What do helper T cells do?
Helper T cells are not able to destroy infected cells directly. Once they recognise a foreign cell or antigen-presenting cell, they become activated, triggering the release of cytokine. At the same time, the activated cells start to divide repeatedly, making many clones which also release cytokine to attract other T and B cells. Some divided clones stay around as memory cells.
41
How do cytotoxic T cells become activated?
When a T cell bearing a specific antigen receptor combines with its complementary antigen on a pathogen or antigen-presenting cell, clonal selection and multiplication of Tc cells occurs, producing:
- clones of activated Tc cells
- clones of memory Tc cells
42
What do the activated Tc cells do?
release chemicals which perforate the pathogen's membrane, allowing further chemicals to access the invader which breakdown the DNA and proteins causing apoptosis
43
What are Tc cells also able to do in terms of cancer cells?
Tc cells are able to recognise antigens found on the surface of cancer cells, attaching to them and bringing about their lysis (bursting).
44
When a B cell finds a complementary set of antigens on an invading pathogen, what is the particular B cell stimulated to do?
multiply rapidly (clonal selection), producing:
- clones of activated B cells (or plasma cells) that can produce antibodies for immediate use
- clones of memory B cells capable of producing antibodies in the future if required.
45
What is the activation of B cells aided by?
helper T cells which are activated by the invading pathogens, releasing cytokines that further stimulate the clonal multiplication of B cells.
46
What do activated B cells undergo?
protein synthesis and manufacture lots of Y-shaped protein molecules (at a rate of 2000/sec) called antibodies, all bearing the same shaped receptor as the B cell.
47
What happens to the antibodies produced by the activated B cells?
These antibodies are released into the lymph and blood plasma which enables them to travel round the body and arrive at the site of infection. Here they combine with antigens on the pathogens to form antigen-antibody complexes. This in itself, is not enough to destroy the pathogen, but does inactivate it (prevent it from invading other cells or tissues) and mark it for destruction by the phagocytes. In other cases, the antigen-antibody complex stimulates a response which results in cell lysis.
48
What happen once T and B cells have completed their job?
the majority undergo apoptosis, however, a few cells stay around as memory cells, which will remain on hand to respond should the same antigen reappear at some time in the future. This gives rise to IMMUNOLOGICAL MEMORY.
49
Describe what is meant by the primary response?
When a pathogen infects the body, it takes time to raise an immune response and select the correct T and B cells (clonal selection) and produce antibodies. Very often the primary response is too slow to prevent the pathogen causing illness
50
Describe what is meant by the secondary response?
If the person survives the primary response and they come across the same pathogen a second time. they have memory Tc, Th and B cells. These cells proliferate and differentiate much quicker, producing clones bearing the correct antigen receptor, to neutralise the pathogen before the person feels unwell.
51
Describe 3 features of the secondary immune response?
Higher concentration of antibodies
faster production of antibodies
higher concentration of antibodies last for a longer time.
52
For blood group A state the following:
- antigens present on rbc
- antibodies present in plasma
- can donate blood to
- can receive blood from
- A
- B
- A, AB
- A, O
53
For blood group B state the following:
- antigens present on rbc
- antibodies present in plasma
- can donate blood to
- can receive blood from
- B
- A
- B, AB
- B, O
54
For blood group AB state the following:
- antigens present on rbc
- antibodies present in plasma
- can donate blood to
- can receive blood from
- A, B
- NONE
- AB
- ALL
55
For blood group O state the following:
- antigens present on rbc
- antibodies present in plasma
- can donate blood to
- can receive blood from
- NONE
- A,B
- ALL
- O
56
Why is blood group O said to be the universal donor?
its red blood cells have no A or B antigens which may be recognised as non-self by the recipient's immune system
57
Why is blood group AB said to be the universal recipient?
Its blood plasma contains no antibodies against the A or B antigens on red blood cells
58
What is the second type of blood grouping antigen that can also be carried on our red blood cells?
D antigen
59
If someone possess the D antigen on their rbc's what are they said to be?
rhesus positive (Rh+)
60
If someone lacks the D antigen on their rbc's what are they said to be?
rhesus negative (Rh-)
61
What problem arises if someone is Rh-?
since their immune system has never met the antigen (as it is non-self), it would mount an immune response against it if it were introduced into their bodies via a blood transfusion
62
What is meant by autoimmunity?
Normally, the body learns to recognise its own (self) antigens from an early stage. However, sometimes the immune system fails to tolerate the self antigen on a certain group of cells or tissue and therefore stimulates T lymphocytes to launch an attack on these cells
63
What does autoimmunity give rise to? Give 3 examples.
autoimmune diseases e.g. rheumatoid arthritis
multiple sclerosis
type 1 diabetes
64
What happens to cause rheumatoid arthritis?
body attacks synovial membranes in joints
65
What happens to cause multiple sclerosis?
body attacks myelin sheath around axon of neurons
66
What happens to cause type 1 diabetes?
body attacks insulin-producing beta cells
67
What is an allergic reaction?
the body overreacts to a normally harmless substance (e.g. pollen, dust or penicillin) by making a hypersensitive response. B lymphocytes respond by making antibodies, which trigger the additional release of histamine from mast cells particularly in the nasal passages and lungs.
68
What treatment is given to an allergic reaction?
anti-histamine medication
69
What is an infectious disease?
one that is capable of being transmitted from one person to another by direct or indirect contact.
70
What is epidemiology?
the study of the characteristics of an infectious disease
71
What are pathogens?
agents which can cause infectious diseases
72
Give 5 examples of pathogens?
```
viruses
bacteria
fungi
protozoa
multi-cellular parasites
```
73
What are the 6 ways pathogens can be transmitted?
direct physical contact (e.g. shaking hands)
inhaled air (e.g.breathing in microbes)
indirect physical contact (sharing contaminated syringe needles)
exchanging body fluids (saliva during kissing)
faecal-oral route (consuming contaminated food/drink)
vector organisms (bitten by mosquito infected with malaria)
74
Give details on how measles could be transmitted?
Air borne
Droplets released during coughing.
Nasal passages heavily congested > droplets released directly into air due to laboured breathing
75
Give details on how HIV could be transmitted?
Body fluids
blood (sharing contaminated needles)
Semen (unprotected sex)
76
Give details on how cholera could be transmitted?
Water borne
direct contact
Drinking water supply becomes polluted with sewage contaminated with cholera bacteria
Consumption of food contaminated by insect vectors (e.g. flies) that have been in contact with sewage containing cholera microbes.
77
What are the 4 ways of controlling transmission of infectious diseases?
Antisepsis
quarantine
individual responsibility
community responsibility
78
What is antisepsis? give examples
the inhibition or destruction of microorganisms that cause disease or decay
e.g. wearing sterile gloves and masks
applying antiseptics to wounds
sterilising equipment before use.
79
What does quarantine involve?
isolating the person who is infected or has been in contact with an infectious source to prevent the spread of the disease.
80
What does individual responsibility include?
1. practicing good hygiene by washing hands, showering, brushing teeth
2. taking care of sexual health to prevent STD
3. handling and storing foods safely at appropriate temperatures and by washing hands before preparation or keeping raw and cooked foods separate.
81
What does community responsibility include?
1. a clean water supply which has been filtered and chlorinated to prevent growth of disease-causing micro-organisms (e.g. cholera), as well as methods to deal effectively with sewage and so preventing it entering our drinking water supply.
2. safe food webs where food producers adopt good practice such as milk pasteurisation, good manufacturing practices and inspections, traceability of food sources.
3. waste disposal mechanisms so our household waste is collected regularly and recycled, incinerated or buried.
4. control of vectors so that any animals which carry pathogens are eradicated e.g. using insecticides to kill mosquitoes infected with malaria
82
What does epidemiology include (3)
1. Locating the initial outbreak of the disease.
2. Studying the pattern and speed of spread
3. Looking at the disease's geographical distribution
83
What is meant by sporadic?
occurs in scattered/ isolated instances with no connection between them.
84
What is meant by endemic?
recurs as a regular number of cases in a particular area
85
What is meant by epidemic?
affects an unusually high number of people in a particular area
86
What is meant by pandemic?
occurs as a series of epidemics spreading across continents or the whole world
87
When an infectious disease is found to be spreading rapidly, what control measures would epidemiologists introduce to try and limit further spread? (3)
preventing transmission between people and areas
using appropriate drug therapy (for those already infected)
immunising people not infected
88
What is immunisation?
the process by which a person develops immunity to a disease-causing organism
89
What is a vaccination?
a method of immunisation which involves deliberately introducing a weakened or altered form of a pathogen (or its toxin)
90
What is a vaccine?
a preparation, usually injected into the body which is designed to illicit an immune response
91
What are the 4 main types of preparation that vaccines usually contain?
dead pathogens
weakened (attenuated) pathogens
parts of pathogens
inactivated toxins
92
What is meant by dead pathogens? Give example
the pathogen has been destroyed and can no longer replicate e.g. polio
93
What is meant by weakened (attenuated) pathogens?Give example
the pathogen has been altered so it can no longer cause the disease e.g. measles
94
What is meant by parts of pathogens? Give example
only the protein coat bearing antigens is used e.g. hepatitis B
95
What is meant by inactivated toxins? Give example
the toxins produced by the pathogens are injected after being inactivated e.g. tetanus
96
In a vaccine what is the preparation usually mixed with?
an adjuvant
97
What is an adjuvant?
a chemical substance that promotes the activity of the antigen and ENHANCES THE IMMUNE RESPONSE
98
How do vaccines work?
Vaccines deliberately introduce the non-self antigen to induce the primary response. They do not cause disease symptoms as a functioning pathogen is not introduced. A vaccinated person who then goes to encounter the actual pathogen will have the same secondary response as someone who has the disease.
99
When does active immunity occur?
when a person makes their own antibodies against a pathogen. This can happen both naturally and artificially.
100
What is natural immunity?
when a person survives an infection and makes immunological memory
101
What is artificially immunity?
when a vaccine is used to trigger immunological memory
102
What are vaccines subject to?
clinical trials in the same ways as other pharmaceutical medicines to establish their safety and efficacy before being licensed for use?
103
Give 3 examples of trial features?
placebo controlled
randomised
double blind
104
Give the description of placebo controlled?
subjects in control group are given a 'sham' treatment lacking the active ingredient
105
Give the description of randomised?
Name, age, gender of participants are withheld to eliminate bias.
Participants are randomly divided into 2 groups.
106
Give the description of double blind?
Neither doctors or subjects know who is receiving what
107
Why is one group given a placebo?
to allow a valid comparison
108
Why must the groups be of suitable size?
to reduce the magnitude of experimental error
109
What are the results from the two groups compared to determine?
whether there any statistically significant differences between the two groups.
110
What is herd immunity?
principle by which many vaccinated individuals protect those that are unvaccinated as they are less likely to come into contact with an infected individual
111
What is meant by herd immunity threshold?
this is the percentage of the population who need to be vaccinated to offer protection for people who are not vaccinated.
112
What does the herd immunity threshold depend on? (3)
the disease virulence - capacity to cause disease
The vaccine efficacy - its effectiveness
the population contact parameters - population density
113
What do most countries have and what does this help do?
a public health policy which helps establish herd immunity (i.e. major vaccination programmes)
114
Why do some countries not have public health policies and widespread vaccination?
due to higher levels of malnutrition and poverty (in the developing world)
115
What can herd immunity be threatened by?
when vaccines are rejected by a percentage of the population (in the developed world) due to adverse publicity
116
What are the 2 main strategies in which pathogens evade the immune system?
Antigenic variation
| Directly attack the immune system
117
What is meant by antigenic variation?
some pathogens can change their antigens to avoid the effect of immunological memory. This usually occurs via random mutations (antigens are protein markers) and since the new antigen structure allows the pathogen to escape the antibodies made against its predecessor in the immune system, it survives and reproduces, giving rise to an increased proportion of this pathogen. This is the case with diseases such as malaria and the flu virus
118
When some diseases (e.g. HIV) attack specific cells in the immune system, what do they do? Give examples
reduce its capability to react against the pathogen. HIV targets T lymphocytes meaning they are unable to attack the pathogen, allowing AIDS to develop. Tuberculosis targets phagocytes , avoiding detection by them
