Immune response Flashcards
1
Q
What is an antigen?
A
Proteins on the cell membrane or wall of a microorganism that is recognised by non self by the immune system and triggers and immune response
2
Q
What are the two types of immune response?
A
Specific and non-specific
3
Q
What type of cells are always involved in immune response?
A
White blood cells
4
Q
What are three types of WBCs?
A
Phagocytes
T lymphocytes
B lymphocytes
5
Q
What can trigger an immune response?
A
- Pathogens
- Cells from other organisms
- Abnormal/Cancerous/Tumour Cells
- Cells infected by a virus
- Injected antigens e.g. vaccines
- Your own cells, in the case of autoimmune disease
6
Q
What is a pathogen?
A
A microorganism that causes disease.
7
Q
Types of pathogens
A
Bacteria
Viruses
Fungi
Protists
8
Q
How do pathogens cause disease?
A
- Producing toxins
- Damaging cells, by replicating inside them and causing them to burst
- Escaping the immune system and spreading to other parts of the body
9
Q
What type of WBC is involved in non specific response
A
Phagocytes
10
Q
What type of WBC is involved in specific response
A
Lymphocytes
11
Q
What is phagocytosis
A
Ingestion of pathogens by phagocytes
12
Q
How phagocytes find pathogens?
A
Phagocytes are attracted to chemicals that are released by pathogens.
13
Q
Steps to phagocytosis:
A
- Phagocyte binds to the foreign antigen of the pathogen and phagocytosis occurs, creating a phagosome (a vesicle containing a pathogen).
- Lysosome containing lysozyme enzymes fuses with a phagosome and lysozymes hydrolyse the pathogen
- Soluble breakdown products are absorbed into the cytoplasm of the phagocyte and antigens can be presented on the surface
14
Q
Difference between specific and non-specific immune response
A
- Specific responses react to specific antigens and are initially slower in action but lead to long term resistance. - Non-specific responses are quicker and respond to any foreign antigen, but do not provide immunity.
- Specific responses depend on lymphocytes
- Non-specific responses depend on phagocytes
15
Q
What are the two types of lymphocytes?
A
B lymphocytes
T lymphocytes
16
Q
Why are B Lymphocytes named as such?
A
They are named B cells because they mature in the bone marrow.
17
Q
Why are T Lymphocytes named as such?
A
They are named T cells because they mature in the thymus gland.
18
Q
What are the two types of T Lymphocyte?
A
Helper T cells and Cytotoxic T cells
19
Q
What is cell mediated immunity/cellular response and which lymphocytes are associated with it?
A
T cells are associated with cell mediated immunity which is the response against cellular foreign bodies.
20
Q
What is humoral immunity and which lymphocytes are associated with it?
A
B cells are associated with humoral immunity which is the response against non cellular foreign bodies.
21
Q
What type of cells do T cells respond to and why?
A
- Foreign/Transplanted Cells – because they have different antigens to self-cells
- Virus infected cells – because they have viral antigens on their surface
- Cancer cells – because they have different antigens
- Phagocytes that have engulfed pathogens – because they present foreign antigens on their surface
22
Q
Steps involved in cellular response:
A
- Helper T cell with a complementary receptor binds to the foreign antigen
- Th is then activated and undergoes mitosis
- Activated Th will then either:
- Develop into memory cells that enable rapid response upon reinfection
- Stimulate more phagocytosis
- Stimulate B cells to divide and secrete antibodies
- Activate cytotoxic T cells
23
Q
How do cytotoxic T cells kill abnormal/infected cells?
A
By producing a protein called perforin that makes holes in the cell surface membrane of these cells, making them freely permeable to everything and the cell dies.
24
Q
How does the action of cytotoxic T cells demonstrate the importance of the cell surface membrane?
A
The action of perforin produced by cytotoxic T cells highlights the importance of the cell surface membrane in maintaining the integrity of cells and hence their survival, as they die when freely permeable.
25
What is a monoclonal antibody?
Identical antibodies that have been produced by an immune cell that has been cloned from a parent cell
26
What is an antibody?
Y shaped proteins synthesised by B cells in response to foreign substances, such as viruses or bacteria
27
Steps to humoral response:
1. A specific B-Lymphocyte with complementary antibodies takes in surface antigens of a pathogen via endocytosis.
2. The B cell presents the foreign antigen on the cell membrane
3. Activated helper T cells will bind to presented antigens and trigger B cells to undergo mitosis
4. Some B cells will become plasma cells and secrete antibodies
5. Others will become memory cells which persist in blood plasma and tissue fluid and will rapidly divide into plasma cells upon reinfection
28
What is the primary immune response?
The production of antibodies by plasma cells and of memory cells
29
What is the secondary immune response?
The rapid division and development of memory cells into plasma cells which make antibodies, and more memory cells upon reinfection
30
Which is faster, primary or secondary immune response, and why?
Secondary, because of the presence of memory cells
31
Key difference between the role of T cells in specific responses
- In the cellular response, Helper T Cells are activated and undergo mitosis
- In the humoral response, Helper T Cells activate B cells and the B cells undergoes mitosis.
32
How many polypeptide chains are antibodies made of and what are their names?
4 chains, 2 heavy chains and 2 light chains
33
How many binding sites does each antibody have?
2
34
What holds heavy and light chains together in an antibody?
Disulphide bridges
35
What are the variable and constant regions on an antibody?
Variable region is the binding site as it differs between antibodies
Constant region is the rest of the antibody
36
What does the variable region on an antibody bind to and what does it form?
Binds to an antigen to create an antibody antigen complex
37
What does the constant region on an antibody bind to?
Receptors on B cells
38
How do antibodies lead to the destruction of antigens?
- Cause agglutination of bacterial cells, which makes it easier to for phagocytes to find as they’re less spread out through the body.
- They serve as markers that stimulate phagocytes to engulf bacterial cells to which they’re attached
39
What is agglutination and how do the binding sites on antibodies make it possible?
Agglutination is the clumping together of pathogens, making it easier for phagocytes to find. Agglutination is possible as each antibody has 2 binding sites and can attach to 2 bacterial cells, causing them to clump together.
40
Ethical issues with monoclonal antibodies
- Production of monoclonal antibodies involves the use of mice, giving them a disease. It also involves deliberately giving mice cancer to produce tumour cells, which raises an ethical issue.
- There have been some deaths associated with their use in the treatment of multiple sclerosis, Patients must give informed consent.
- Drug trial involving monoclonal antibodies resulted in organ failure in volunteers.
41
Benefits of monoclonal antibodies
Can be used for pregnancy tests, tests for diseases like HIV, cancer treatment, can be produced quickly.
42
Limitation of monoclonal antibodies
Side effects are worse than anticipated, they’re expensive to produce.
43
Making monoclonal antibodies
1. Mouse is injected with an antigen to stimulate antibody production.
2. B cells are extracted from the mouse
3. These cells are fused with rapidly dividing tumour cells to form hybridomas
4. Hybridomas can produce many antibodies and divide rapidly.
44
Cancer treatment using monoclonal antibodies
1. Cancer cells have antigens called tumour markers
2. Monoclonal antibodies can be made that will bind to the tumour markers, and anti-cancer drugs can be attached to the antibodies
3. When antibodies come into contact with cancer cells, they’ll bind to the tumour markers
4. Meaning the drug will only accumulate around cancer cells.
5. They release chemicals that block signals that stimulate the uncontrolled growth of the cancer cells
6. Side effects are much lower because they accumulate near cancer cells
45
Pregnancy testing using monoclonal antibodies
1. Application area contains antibodies for hCG, which are bound to a coloured bead
2. When urine is applied to the application area, any hCG will bind to the antibody with the beads
3. Forming an antibody-antigen complex
4. Urine moves up the stick to the test strip, carrying any bead with it
5. Test strip contains immobilised hCG antibodies
6. If there’s hCG present, the strip turns blue because the immobilised antibody will bind to the antibody antigen complex, saturating the strip with hCG antibody with the blue beads attached. If no hCG is present, the beads will pass without binding, so it won’t go blue.
46
What does ELISA stand for?
Enzyme Linked Immunosorbent Assay
47
ELISA test for HIV
1. HIV antigen is bound to the bottom of a well in a well plate
2. A sample of the patient’s blood plasma is added to the well. HIV specific antibodies will bind to the antigen and remain at the bottom of the well
3. Well is washed out to remove unbound antibodies
4. Secondary antibodies with a specific enzyme attached are added to the well. These antibodies can bind to the HIV specific antibody.
5. The well is washed out again to remove and unbound secondary antibodies.
6. A solution containing a substrate which will bind to the enzyme and create a coloured product is added. If the solution changes colour, then HIV antibodies are present in the patient’s blood plasma, and they are infected with HIV.
48
What does HIV stand for?
Human Immunodeficiency Virus
49
What does AIDS stand for?
Acquired Immune Deficiency Syndrome
50
What does reverse transcriptase do?
Catalyses the production of DNA from RNA
51
Components of HIV
Attachment Proteins
Capsid
Lipid envelope
Viral RNA
Reverse transcriptase
52
Replication of HIV
1. HIV uses attachment proteins to bind to complementary receptors on helper T cells.
2. Virus enters Helper T cells
3. Viral RNA and reverse transcriptase are released into the cell
4. Reverse transcriptase converts viral RNA to DNA
5. Newly made viral DNA moves into the nucleus of host cell and is inserted into host cell DNA
6. Viral DNA creates mRNA containing instructions to make new viral RNA, capsids and reverse transcriptase
7. Proteins are made using host ribosomes from viral mRNA
8. New virus particles are assembled
9. HIV particles burst out of host cell, breaking a piece of its cell surface membrane to make their lipid envelope
53
How does HIV cause AIDS?
HIV attacks helper T cells. Without enough helper T cells, B cells can’t be activated to produce antibodies or cytotoxic T cells that kill antibodies. As a result, the body is more susceptible to secondary infections as the immune response is inadequate.
54
How do antibiotics work?
Antibiotics work by stopping bacteria from making cell walls by inhibiting the enzymes required for their synthesis. This weakens cells walls making them unable to withstand pressure. This way, when water enters by osmosis, bacterial cells burst and die.
55
Why don't antibiotics work on viral infections?
Viruses rely on host cells to carry out metabolic activities, so antibiotics are ineffective as there’s no metabolic mechanisms or cell structures for them to disrupt.
56
What is immunity?
The ability of an organism to resist infection.
57
How is passive immunity produced?
Produced by the introduction of antibodies from an outside source.
58
Why is passive immunity short lived?
The body isn't making its own antibodies so no memory cells are formed
59
What are the two ways to gain immunity?
Vaccination and exposure
60
How is active immunity produced?
Produced by stimulating the production of antibodies by the individuals own immune system, by infecting an individual with the disease
61
What is natural active immunity?
Results from becoming infected by a disease under normal circumstances. The body produces its own antibodies and may do so for years.
62
What is artificial active immunity?
Forms the basis of vaccination. Inducing an immune response without suffering symptoms.
63
What is vaccination?
Vaccination is the introduction of the appropriate antigens/pathogens into the body in their dead or inactive form.
64
What is herd immunity?
An immunity that arises when most or all of a population has been vaccinated meaning it is difficult for the disease to spread and highly unlikely that someone will encounter an infected individual
65
Features of a successful vaccination programme
- Enough of the vaccine to immunise a large population
- No/few side effects to avoid discouraging the population from being immunised
- Means of producing, storing and transporting the vaccine
- Effective way of administering the vaccine in large populations
- All or most of the population must be vaccinated to achieve herd immunity
66
Why might a vaccination programme not eliminate a disease?
- Some people may have defective immune systems
- If the disease is caught shortly after vaccination, the immune system won’t have built up resistance
- Pathogen may mutate frequently, and the vaccine will become ineffective because.
- Vaccines may be against 1 strain of a disease that has 100 strains
- Some pathogens hide in body cells or body parts, concealed from the immune system
- Individuals may refuse vaccination for medical, ethical, religious or daft reasons.
67
What is antigenic variability and what problems does it cause?
When pathogens mutate frequently and their antigens change. This means that immunity against disease is short lived because the body won't have antibodies against the new antigen
68
Ethical issues of vaccines
- Tested on animals
- Testing on people can be tricky
- Some people may not want to take the risk of side effects
- Is it acceptable to trial with unknown health risks?
- Should expensive vaccination programmes be continued when a disease is almost eradicated?
