Immunology Flashcards
(71 cards)
1
Q
What do proteins on the surface of a cell allow the immune system to recognise
A
- pathogens
- non-self material such as cells from other organisms of the same species
- toxins
- abnormal body cells (eg cancer cells)
2
Q
What are 2 types of white blood cells
A
Phagocytes and lymphocytes
3
Q
What do phagocytes do
A
Ingest and destroy the pathogen
4
Q
What do lymphocytes do
A
Are involved in immune responses
5
Q
What are the 2 types of defence mechanisms
A
Non specific and specific
6
Q
What is a non specific defence mechanisms
A
Response is immediate and the same for all pathogens
7
Q
What is a specific defence mechanisms
A
Response is slower and specific to each pathogen
8
Q
What are examples of a non specific defence mechanisms
A
Physical barriers
Phagocytosis
9
Q
What are examples of specific defence mechanisms
A
Cell-mediated response - T lymphocytes
Humoral response - B lymphocytes
10
Q
How do lymphocytes recognise cells belonging to the body
A
Any lymphocytes that show an immune response to self-antigens undergo programmed cell death (apoptosis) before they can differentiate into mature lymphocytes
11
Q
What is programmed cell death called
A
Apoptosis
12
Q
What are the steps of phagocytosis
A
- The phagocyte is attracted to the pathogen by chemical products of the pathogen -> it moves towards the pathogen along a concentration gradient
- The phagocyte has several receptors on its cell-surface membrane that attach to chemicals on the surface of the pathogen
- The lysosomes within the phagocyte migrate towards the phagosome formed by engulfing the bacterium
- The lysosomes release their lysozymes into the phagosome, where they hydrolyse the bacterium
- The hydrolysis products of the bacterium are absorbed by the phagocyte
13
Q
When are phagosomes formed
A
When phagocytes engulf pathogen to form a vesicle
14
Q
What is an antigen
A
A protein found on the cell surface membrane that stimulates an immune response
15
Q
Where are lymphocytes produced
A
By stem cells in bone marrow
16
Q
What are the 2 types of lymphocytes
A
B lymphocytes (B cells)
T lymphocytes (T cells)
17
Q
Why can T cells distinguish non-self material
A
- phagocytes that have engulfed and hydrolysed a pathogen present some of a pathogens antigens on their own cell membrane
- invaded body cells present some of the viral antigens on their own cell membrane
- transplanted cells from individuals of the same species have different antigens
- cancer cells are different from normal body cells and have antigens
18
Q
What are antigen-presenting cells
A
Cells that display foreign antibodies on their surface
19
Q
Response of T lymphocytes
A
- Pathogens invade body cells or are taken in by phagocytes
- The phagocyte places antigens from the pathogen on its cell membrane
- Receptors on a specific helper T cell fit exactly onto these antigens
- This attachment activates the T cell to divide rapidly by mitosis and form a clone of genetically identical cells
- The cloned T cells then do many things
20
Q
What do the cloned T cells do
A
- develop into memory cells
- stimulate phagocytes to engulf pathogens (phagocytosis)
- stimulate B cells to divide and secrete their antibody
- activate cytotoxic T cells
21
Q
What do cytotoxic T cells do
A
Kill abnormal cells and body cells that are infected by pathogens, by producing a protein called perforin that makes holes in the cell membrane
-> these holes mean the cell membrane becomes freely permeable to all substances and the cell dies as a result
22
Q
What do humoral immunity involve
A
- involves antibodies that are soluble in blood and tissue fluid
- each B cell produces 1 particular antibody that responds to 1 specific antigen
23
Q
What is clonal selection
A
When a B lymphocyte/cell divides by mitosis to form a clone of identical B cells, all of which produce the antibody that is specific to the foreign antigen
24
Q
What are the antibodies that the B cell clones produce called
A
Monoclonal antibodies
25
In each B cell clone, the cells produced develop into either…
• Plasma cells
• Memory cells
26
What do plasma cells do
Secrete antibodies into blood plasma
-> responsible for the immediate defence of the body against infection
-> this and the production of memory cells is known as primary immune response
27
What do memory cells do
Responsible for the secondary immune response
- don’t produce antibodies directly but when they encounter the same antigen they divide rapidly and develop into plasma cells
-> the memory cells provide long term immunity against the original infection
28
Role of B cells
1. Surface antigens of invading pathogens are taken up by a B cell
2. B cell presents them on its surface
3. Helper T cells attach to processed antigens, so activating the B cell
4. B cell divides by mitosis to give a clone of plasma cells
5. Cloned plasma cells produce specific antibody that fits the antigen exactly
6. Antibody attaches to antigens on pathogen and destroys them
7. Some B cells develop into memory cells
-> these response to future infection by same pathogen - the secondary immune response
29
What cell is involved in cell mediated immunity
T cells
30
What cells are involved in humoral immunity
B cells
31
How many binding sites does an antibody have
Each has 2 identical binding sites
32
What are antibodies made up of
4 polypeptide chains - chains of 1 pair are long and called heavy chains while the chains of the other pair are shorter and called light chains
33
Where do antibodies fit
Each one fits into a specific antigen to form and antigen-antibody complex
34
Is the binding site the same in all antibodies
No it’s different and so called the variable region a
35
What is the rest of the antibody beside the binding site called
The constant region
36
How antibodies destroy antigens
- they bind and cause **agglutination** of bacterial cells
- this clumps bacterial cells together so it’s easier for phagocytes to locate them
- they can serve as markers to stimulate the phagocytes to engulf the bacterial cells to which they’re attached
37
What do antigens on microorganisms entering the body do
Each antigen will induce a different B cell to multiply and form a clone of itself -> each clone will produce different antibodies known as monoclonal antibodies
38
What are the uses of monoclonal antibodies
- targeted medication
- pregnancy testing
- medical diagnosis
39
3 ways of treating cancer with monoclonal antibodies
1. Direct use triggers immune system to recognise, attach and destroy cancer cells
2. Using them to block receptors on the surface of the cancer cells and so stop the cells growing and dividing
3. Can be used to carry toxic drugs or radioactive substances for radiation therapy, or chemicals that stop cells growing and dividing to attack the cancer cells directly without harming other body cells
40
What is immunity
The ability of an organism to resist infection
41
What 2 forms does immunity take
Passive immunity and active immunity
42
What is passive immunity
- The introduction of antibodies from an outside source -> giving immediate immunity
- No direct contact with the pathogen or its antigen is needed to induce immunity
- The antibodies aren’t produced by the individual so they don’t get replaced
- No memory cells formed -> so no lasting immunity
43
Examples of passive immunity
• Anti-venom given to victims of snake bites
• Antibodies passing across the placenta from the mother to the fetus
44
What is active immunity
- Stimulates the production of antibodies by the individuals own immune system
- Direct contact with the pathogen or the antigens necessary
- Immunity takes time to developed but its long-lasting
45
What are 2 types of active immunity
1. Natural active immunity
2. Artificial active immunity
46
What is natural active immunity
When the individual is infected with the disease and the body produces its own antibodies and continues to do so for years
47
What is artificial active immunity
This is the basis of vaccination
- involves inducing an immune response without suffering the symptoms of the disease
48
How do vaccinations work
- it’s the introduction of the appropriate disease antigens into the body, either by injection or by mouth
- the vaccine contains 1 or more types of antigen from the pathogen which stimulate and immune response
- the response is small due to the small amount of antigen used
- memory cells are produced that remain in the blood and allow a greater, quicker response to future infection with the pathogen
- the result is a rapid production of antibodies
49
Features of a successful vaccination program
- Economic availability of vaccine in sufficient amount to immune most of the vulnerable population
- Must be few side-effects, if any - may discourage individuals in a population
- Means of producing,storing and transporting the vaccine must be available
- Must be the means of administering vaccine properly at the appropriate time
- Must be possible to vaccinate the vast majority of the vulnerable population to produce herd immunity
50
Why vaccinations mightn’t eliminate disease
- Fail to induce immunity in certain individuals
- Individuals may develop the disease immediately after vaccination but before their immunity is high enough to prevent it
- Pathogen may mutate frequently, so antigens change suddenly rather than gradually -> this antigenic variability happens with the influenza virus, immunity is therefore short-lived
- May be so many varieties of a pathogen a vaccination can’t be made for them all
- Certain pathogens hide from immune system
- Objections like for religious, ethical or medical reasons
51
Ethics of vaccines
- Use of animals
- Side-effects can cause long-term harm
- Who should they be tested on
- Should it be compulsory
- Cost of vaccination programmes
52
Structure of HIV
- RNA
- Reverse transcriptase
- Intergrase
- Matrix
- Lipid envelope
- Capsid
- Protein coat -> attachment proteins
53
What does reverse transcriptase do
Converts RNA to DNA
54
What does intergrase do
Catalyses the integration of the viral DNA made by reverse transcriptase into the host cell’s genome
55
Explain why viruses are described as acellular and non-living
Not made of cells and can’t replicate independently
56
What is present in ALL viruses
Guanine
57
How does HIV enter a host cell
1. **Binding**
HIV attachment proteins bind to the complimentary CD4 receptor on the helper T cells
2. **Fusion**
HIV RNA, reverse transcriptase, viral proteins released when cell surface membrane fuses with T helper cell
3. **Reverse transcriptase**
Forms viral DNA from RNA
4. **Integration**
Viral DNA goes into nucleus and integrated into the host DNA/genome
5. **Replication**
All new viral RNA formed is used to make all the viral proteins
6. **Assembly**
All the parts of the virus are put together
7. **Budding**
Virus is released
58
59
What does the ELISA test stand for
Enzyme linked immunoabsorbant assay
60
What does the ELISA test do
It uses antibodies to detect the presence and quantity of protein in a sample
61
Why is the ELISA test good
It’s very sensitive and can detect very small amounts of molecule
62
ELISA test procedure
1. Apply the sample to a surface to which all antigens in the sample will attach
2. Surface is washed to remove any unattached antigens
3. Add antibody that’s specific to the antigen we are trying to detect
4. Wash surface to remove excess unbound antibodies
5. Add a 2nd antibody that binds with the first antibody -> this is enzyme linked
6. Add the colourless substrate of the enzyme
7. If present enzyme converts substrate to coloured product
63
In the ELISA test the amount of antigen present is relative to..
The intensity of colour that develops
64
What can the ELISA test be used to detect
HIV and the pathogens of diseases
65
What is a way antibiotics work
By preventing the bacteria from making a cell wall
66
How do antibiotics work
They inhibit certain enzymes that are needed for the synthesis and assembly of the peptide cross-linkages in bacterial cell walls
-> this weakens the walls, so they can’t withstand pressure from water entering - so the cell bursts and dies
67
Why are antibiotics ineffective with viruses
Because there are no metabolic mechanisms or cell structures for them to disrupt
-> viruses have a protein coat and no murein wall (like bacteria do) and are also within an organisms cells so antibiotics can’t reach them
68
Give 2 reasons why the ELISA test cannot be used to find out if a person has AIDS
1. AIDS related symptoms
2. Number of helper T cells
69
A baby tested positive for the ELISA test doesn’t prove it has HIV. Why?
Children/babies receive antibodies from their mothers so colour will always turn blue initially
70
Why would a control well with salt solution instead of blood plasma be important
1. Shows that there’s nothing else causing the colour change
2. Washing is ineffective/all in our antibody is washed away
71
Why is the cell mediated response specific
Because T cells respond to antigens on the surface of cells
