Immune System Flashcards
1
Q
What is a pathogen?
A
Any microorganism that causes disease
2
Q
Give examples of pathogens
A
- bacteria
- virus
- protists
- fungi
3
Q
What are the two types of defence mechanisms
A
- specific
- non specifc
4
Q
What is a non specific defence mechanism?
A
Response is immediate and the same for all pathogens
5
Q
What is a specific defence mechanism
A
A slower response as it’s specific/targeted to each cell
6
Q
What are two types of non-specific defence?
A
- physical and chemical barriers
- phagocytosis
7
Q
Give an example of a physical/chemical barrier
A
- Hydrochloric acid in the stomach
- mucus and cilia in the trachea
- lysosomes in tears
8
Q
What are the two types of specific defence mechanisms?
A
Cell mediated response (T-cells)
Humoral response (B-cells )
9
Q
What is an antigen?
A
A molecule (often a protein) that the body recognises as foreign so triggers an immune response.
10
Q
What does the immune system have the ability to do?
A
Distinguish between self and non-self cells (foreign materials)
11
Q
How to autoimmune diseases occur?
A
If the immune system goes wrong it can begin to attack self cells causing autoimmune symptoms
12
Q
Give an example of an autoimmune disease
A
Multiple sclerosis
(Myelin sheath of neurones are damaged)
13
Q
How does the body distinguish between self and non self cells?
A
Each type of cell has specific molecules (antigens) on its surface that identify it
These molecules are usually protein as their 3D tertiary structure enables unique identifiable structures to form on the surface.
14
Q
What are the non self cells that trigger the immune response?
A
Pathogens
Cells from other organisms same species (transplants)
Abnormal body cells
Toxins
15
Q
What causes antigen variability?
A
Mutations of the DNA - which occurs in the gene coding for the antigen causes its tertiary structure to change shape.
16
Q
What does antigen variability mean for immunity?
A
Previous immunity is no longer effective as memory cells in the blood will only have a memory of old antigen shape.
17
Q
When are lymphocytes made?
A
Foetus
18
Q
How are lymphocytes used to generate immunity as a foetus?
A
Lymphocytes complimentary to the antigens on self-cell walls will die or production will be suppressed ( this is to prevent your lymphocytes from attacking your own cells)
19
Q
After birth where are lymphocytes created?
A
Bone marrow
20
Q
Describe the process of phagocytosis?
A
Chemicals are released by the pathogen
The phagocytes are attracted to these chemicals (foreign substances) and move towards the pathogen
The phagocyte engulfs the pathogen into a vesicle called a phagosome (by endocytosis)
Lysosomes found in the phagocyte move towards the vesicle and fuse with the phagosome
Lysozymes (hydrolytic enzymes) in the lysosomes digests the pathogen
The phagocyte displays the important antigens on its cell surface membrane
21
Q
What is an antibody?
A
A protein with specific binding sites complimentary to a specific antigen, synthesised and secreted by plasma cell.
22
Q
What type of structure do antibodies have?
A
They are a Y - shaped protein
Made up of 4 polypeptide chains held together by disulphide bridges
X2 heavy chains and x2 light chains
23
Q
How does an Antigen - Antibody Complex form?
A
When an antibody collided with a foreign cell that possess non-self antigens with a complimentary shape, it binds with one of the antigens.
24
Q
What type of structure do antibodies have?
A
A specific 3D tertiary structure
The antigen binding sites are variable regions which are complimentary to one specific antigen as they are made of a specific amino acid sequence.
25
How does antibodies lead to the destruction of pathogens?
Agglutination
26
What is agglutination
Agglutination is when antibodies each bind to an antigen on two separate pathogens, causing the pathogens to clump together via a network of antigen-antibody complexes.
This clump is then easier for phagocytes to locate and engulf. The antibodies also serve as a marker for the phagocyte to commence phagocytosis of the bacteria.
27
What are MABs?
Monoclonal antibodies- antibodies with the same tertiary structure produced from a genetically identical set of plasma cells - antibodies are all specific to the same antigen
28
What type of lymphocyte does the cell mediated response use
T lymphocytes
29
What type of lymphocytes does the humoral response use
B lymphocytes
30
Where are B and T cells produced?
Bone marrow
31
Where do T cells mature?
Thymus gland
32
Approximately, how many types of B/T cells are there?
- 10 million (of each)
33
Explain the process of the cell mediated response
- The invading pathogen is engulfed by the phagocyte , the lysosomes within the phagocyte digest the pathogen in the phagosome, and is presented on the cell surface membrane (becoming an APC)
- The T-cell with a complimentary surface receptor binds to the APC
- This stimulates/activates the T cells causing them to divide by mitosis and form clones.
- some T cells become memory T cells, some become cytotoxic/killer T cells which release cytotoxic to kill infected cells, some become suppressor T cells which release cytokines to stimulate phagocytosis, some become helper T cells which bind to antigen presenting B cells which stimulates the B cells causing them to divide by mitosis. Some B cells become memory B cells while some become plasma B cells, which secrete antibodies complimentary to the antigen the B cell presents on its surface.
34
What are the 4 different types of T cells which form?
- Memory T cells
- Suppressor T cells
- Cytotoxic T cells
- Helper T cells
35
How does the humoral response work?
- B cells with complimentary surface antibodies bind to antigens in solution
- The antigens are injested and processed before being displayed on their cell surface membrane
- Helper T cells bind to the antigen on the B cell surface, stimulating B cells to divide by mitosis
- These B cells then become memory B cell or Plasma B cells which produce complimentary Antibodies displayed on the B cell surface
36
What are the two types of B cells which form?
- memory B cells
- plasma B cells (produce antibodies)
37
What are monoclonal antibodies?
Antibodies with identical tertiary structure produced by genetically identical plasma cells that are all specific to one antigen
38
How are MABs artificially produced?
A mouse is injected with a dead/attenuated antigen form of a microorganism which triggers an immune response.
The plasma cells are harvested from its liver
The plasma cells are fused with tumour cells to create Hybridoma cell- which divide uncontrollably and produce specific antibodies
39
What are the three different uses of MABs?
Targeting medication to specific cell types
Medical testing
Medical diagnosis using ELISA
40
What are the two types of targeted medication for specific cells
Direct monoclonal antibody therapy
Indirect monoclonal Antibody therapy
41
How does direct monoclonal antibody therapy work?
MABs are produced which are specific to the antigen on the target cell (e.g cancerous cell)
The antibodies are given to the patient and they bind to the antigen on the target cell
This prevents their uncontrolled growth by blocking growth signalling pathways
42
What is indirect MAB therapy?
- a cytotoxic drug is attached to the monoclonal antibody
- this antibody is given to the patient and binds to the complimentary antigens on the surface of the target cell
- The target cell is killed as the cytotoxin is released
43
What are the practical applications of medical testing with MABs?
Pregnancy test
COVID
44
What is the purpose of pregnancy test?
To detect the hormone HCG in the urine
45
What are the three sites of a pregnancy test strip?
- reaction site
- test site
- control site
46
What happens at the reaction site of a pregnancy test strip?
It contains mobile anti-HCG antibodies (which are bound to an enzyme/ coloured bead) that are complimentary to the HCG hormone (protein)
If the HCG hormone is present it will bind to the anti-HCG antibody at the binding site
47
How does urine move up the test strip?
By capillary action
48
What happens at the test site of a pregnancy test strip?
- contains fixed/immobilised anti-HCG antibodies and dye molecules
- The anti-HCG antibody binds to the HCG portion of the antigen-antibody complex
- the enzymes linked to the antibody catalyse a reaction with the dye molecules (substrate) and form a coloured product when the E-S complex forms
49
What happens at the control site of pregnancy tests?
Fixed/immobile anti-mouse antibodies
Anti-HCG antibodies (become antigens) that didn’t bind at the test site bind to anti-mouse antibodies and cause a coloured product to form
50
What is the purpose of the control site?
Prove the test has worked/been successful
51
What does ELISA stand for?
Enzyme linked immunosorbent Assay?
52
What is the purpose of ELISA?
A lab technique used to identify the presence and concentration of an antigen or antibody in a patient sample
53
What are the two types of ELISA?
-Direct ELISA
-Indirect ELISA
54
Give a brief overview of what the two types of ELISA are?
Direct- Antibody bound to multi-well plate
Indirect- Antigen bound to multi-well plate
55
Explain how the ELISA test works for HIV diagnoses?
- HIV antigen molecules attached to the walls of the multi well plate
- Adds sample of blood plasma to the well, if HIV antibody is present they will bind to the HIV antigen
- wash out excess antibodies high haven’t bound to the antigen in the multi-well plate
- Add a second antibody with an enzyme attached to it. This binds specifically to the HIV antibody (if present)
- A yellow solution is added which changes blue if the enzyme is present
- the blue colour indicates HIV antibodies are present and the person is HIV positive
56
What does a higher colour intensity indicate in an ELISA test?
A higher concentration of antigen/antibody
57
What control should be used when doing an ELISA test?
- complete test with a salt solution not blood plasma a
58
Why should you do a control experiment for ELISA
- To ensure the only thing causing the colour change is the enzyme
- washing out is effective
59
Ethical issues associated with MABs?
Mice used to produce tumours for antibody production
Informed consent from patients as some deaths linked to use
Clinical trials have significant risks
60
What do vaccines contain?
They contain dead/attenuated antigens of specific microorganisms that induce a primary immune response (producing memory cells) without suffering the symptoms of the disease
61
What is a primary response?
The first encounter/exposure to a specific antigen
62
What is a secondary immune response?
The second exposure to a specific antigen triggers the production of more antibodies, quicker
63
How do vaccines work?
- A dead or attenuated antigen from a specific antigen is inserted into the human body
- phagocytosis occurs and presents it on its cell surface membrane,
- antigens are processed and presented on APC B cells
- the B cell is activated by the T helper cell resulting in mitosis
- This forms clones of memory cells and plasma cells (produce complimentary antibodies)
- the memory cells provide long lasting immunity and is ready for antigen to enter the body again
64
What is here immunity?
When a sufficiently large proportion of population has been vaccinated to make it difficult for a pathogen to spread within that population.
65
Why can’t vaccines eliminate disease?
- certain individuals have defective immune systems
- certain pathogens ‘hide’ from the immune system
- may have religious, medical or ethical obligations.
- antigenic variability
66
What is antigenic variability?
The DNA of pathogens mutate frequently causing changes in the gene sequence causing the shape of the antigen to change and the memory cells no longer able to recognise the antigen
67
What is the difference between antigenic drift and shift?
Antigenic ‘drift’ gradual alteration (poor immune recognition)
Antigenic ‘shift’ significant alteration in shape (no immunity = no recognition)
68
What are the ethical consideration for a vaccine
Economically viable
Enough cover population in order to obtain herd immunity where possible
Produce, store and transport efficiently and without damage
Organised administration with trained staff
69
What are the 4 types of immunity?
Passive
Active
Artificial
Natural
70
What is passive immunity?
Introducing or inserting MAB into an organism from an outside source- no contact with the pathogen or its antigens
71
Give an example of passive immunity?
- blood transfusion
- maternal antibodies from breast milk
72
What is active immunity?
Involves direct contact with the pathogens/antigens stimulating the body’s immune system to produce its own antibodies
73
Give an example of active immunity?
- vaccines
- coming into contact with pathogen
74
Compare the differences between active and passive immunity
Active: produce antibodies via plasma cells, involves memory cells, longer term protection due to memory cells, takes longer to develop/create
Passive: antibodies introduced into body from outside, short-term no memory cells made and antibodies break down, short-term
75
Describe a successful vaccination?
- financially available
- few/no side effect
- sustained way of producing, storing and transporting
- ways of administering it properly
- sufficient quantities to vaccinate (for herd immunity)
76
What does HIV stand for?
Human immunodeficiency virus
77
Describe the structure of HIV
- lipid envelope
- attachment protein
- capsid
- genetic material
- reverse transcriptase
78
What is a retrovirus
A group of viruses where the virus is able to insert its genetic material into a host cell’s DNA using enzyme reverse transcriptase
79
What cell does HIV target?
It targets T helper cells
- because it is a virus (acellular) it requires a host cell to reproduce
80
Explain how HIV replicates
- Virus binds (using attachment proteins) to receptor proteins (CD4) on the surface of helper T cell
- Virus lipid envelope fuses with the cell surface membrane
- The capsid breaks down and release its genetic material (RNA) and enzymes int to cell
- Reverse transcriptase converts RNA into DNA
- The viral DNA moves into the nucleus via a nuclear pore and is inserted into the host cell
- The HIV DNA is transcribed into mRNA and translated into viral proteins
- New viral particles assembles and bud off from the cell surface membrane to infect more cells
(Destroying the helper T cell)
81
When is the AIDs diagnosis given to a patient?
When the helper T cell count drops below 200 cells/mm^3 of blood, when the normal level is 800-1200 cells/mm^3
82
What are AIDs symptoms related to?
Infections (usually secondary) the immune system is unable to deal with as they’re unable to produce adequate immune response
83
After being infected with HIV, the individual develops a number of other infections over the following years. Explain why.
- HIV utilises helper T cells as a host cell and as it replicates, it destroys them
- This leads to a decrease in the number of helper T cells in the blood,
- this means fewer, he,per T cells to activate B cells, which divide by mitosis to form clones of plasma and memory cells
- less/fewer antibodies against pathogens are available to fight secondary infections, so the immune system is unable to fight off pathogens.
84
What is the purpose of the aseptic technique of working close to a Bunsen flame
Allows for upward convection currents to sterilise the air
85
What is the purpose of the aseptic technique of opening the petri-dish as little as possible
Prevent bacteria in the dish getting out and bacteria in the air contaminating the air
86
What is the purpose of the aseptic technique of washing hands with soap?
Prevent contamination from bacteria on hands
87
What is the purpose of the aseptic technique of using a sterile pipettes/flaming bottle necks and glass spreader?
Maintain a pure culture of bacteria
88
What is the purpose of the aseptic technique of disinfecting surfaces?
Kill bacteria on surfaces so contamination doesn’t occur
89
What is the purpose of the aseptic technique of soaking contaminated pipettes tips in disinfectant
To kill bacteria and prevent spreading outside the laboratory
90
Why do some antibiotics create a larger zone of inhibition?
They are more effective at killing bacteria
Diffuse more quickly through the agar
91
If there is no zone of inhibition, what can we conclude about the bacteria?
The bacteria has a anti-biotic resistance
92
What are two statistical tests?
Standard deviation
T-test for
93
How do you right a null hypothesis for a T-test?
There will be no statistically significance between the mean… and any difference I’d due to chance
94
How do you right an alternative hypothesis for T-test?
There will be a statistically significance between the mean… and any difference is not due to chance
95
What is the minimum confidence % required for a statistically significant difference
95%
96
What is the ideal P value for T tests?
P= 0.05
(5%) - could be due to chance
