Topic 2C: Cells and the Immune System Flashcards
1
Q
What is an antigen?
A
- Usually a protein / glycoprotein
- Non-self –> generate immune response
2
Q
Where can non-self antigens come from?
(4 places)
A
- Pathogens
- Abnormal body cells - e.g. cancer
- Cells from other individuals - e.g. transplant
- Toxins
3
Q
How does phagocytosis occur?
A
- Phagocyte recognises non-self antigens
- Phagocyte engulfs pathogen - cytoplasm moves around it
- Pathogen contained in phagocytic vacuole
- Lysosome fuses releasing lysozymes to hydrolyse and break down pathogen
- Antigens can be stuck on surface to be an antigen presenting cell and activate immune cells
4
Q
How do T cells function in the immune system?
A
- Have receptor proteins that bind to complimentary antigens presented by phagocytes
- This activates them
- Cytotoxic - kill foreign and abnormal cells
- Helper - release chemical signals to stimulate phagocytes
–> also activates B cells
5
Q
What do B cells do in the immune system?
A
- Have antibodies that bind to complimentary antigens –> antigen-antibody complex
- With substances from helper T cells they are activated
–> clonal selection - B cell divides to plasma cells –> produce antibodies
6
Q
Describe the structure of an antibody
A
- 2 heavy, 2 light chains
- Constant region, variable region on ends
- Connected by disulphide bridges
- 2 antigen binding sites
7
Q
How do antibodies help immune response?
A
- 2 binding sites so can clump pathogens
–> agglutination - Easier for phagocytosis
8
Q
What is cellular response?
A
- T cells and other immune system cells they interact with –> phagocytes
9
Q
What is humoral response?
A
- B cells, clonal selection, antibody production
10
Q
Describe the primary response
A
- Antigen enters the body for the first time
- Slow - not many b cells to make the correct antibody
- Symptoms show until enough antibody made
- T&B cells make memory cells –> now immune
11
Q
Describe secondary response
A
- Same pathogen re-enters
- Quicker & stronger response - faster clonal selection
- Memory B cells - activate and divide to plasma cells
- Memory T cells - activate an divide to correct type to kill pathogen
- Pathogen fought off before symptoms show
12
Q
What is active immunity?
A
- When the immune system makes it’s own antibodies from an antigen stimulus
13
Q
What is natural active immunity?
A
- Immunity comes from catching an illness
14
Q
What is artificial active immunity?
A
- Immunity comes from a vaccine
15
Q
What is passive immunity?
A
- Given antibodies from another organism
16
Q
What is natural passive immunity?
A
- Baby immune due to mother’s antibodies from placenta and milk
17
Q
What is artificial passive immunity?
A
- Injected with antibodies from someone else e.g. for tetanus
18
Q
What are the features of active immunity?
A
- Longer lasting
- Memory cells produced
- Need exposure to antigen
- Takes longer to form protection
19
Q
What are the features of passive immunity?
A
- Don’t need exposure to antigen
- Immediate protection
- No memory cells produced
- Short term protection
20
Q
What is a vaccine?
A
- Contain pathogen in a weakened, inactive or antigen only
21
Q
How do vaccines work?
A
- Stimulate an immune response
- Produce memory cells without symptoms so you are immune
- If re-infected - quicker and more effective response
22
Q
How can vaccines be taken?
A
- Injection or orally
- Oral - can be broken down by enzymes or be too big to be absorbed into the blood
23
Q
What is antigenic variation?
A
- Antigens on the pathogen changes so it is not detected on second infection
- Have another primary response and are ill again
24
Q
Why does the flu vaccine change every year?
A
- Antigens change every year
- Memory cells from one strain do not work on others
- Immunologically distinct
25
What are ethics of vaccination?
- Animals - tested on animals, can use animal substances
- Side effects - fear or children having side effects
- Epidemics - antivaxxers protected by others - unfair
- Who to vaccinate first in a population
- Which countries should get vaccines first - developing / rich
26
What is herd immunity?
- Susceptible people protected by the immunity of others in the population --> disrupts transmission
27
What is a monoclonal antibody?
- Produced from genetically identical B cells
- Complimentary to antigen - unique tertiary structure
28
How can antibodies treat cancers?
- Cancer cells have tumour markers
- Monoclonals can be specific and bind to these carrying an anti cancer drug
29
How is this treatment good?
- Only targets cancer cells so there are fewer side effects - normal body cells unaffected
30
How do pregnancy tests work?
- Detects hCG
- Application area - hCG ABs with coloured bead attached
- hCG binds - antigen-antibody complex
- Moves up the strip - carries beads
- Test strip has immobilised ABs to hCG
- hCG with AB & bead bind to immobilised AB
- Blue beads make the line
- If no hCG present - antibodies pass through - no line
31
What do ELISA tests do?
- Can see if a patient has a specific antigen or antibody
- Antibodies have enzyme attached that reacts with a substrate to make a colour change
32
What do direct ELISA test for?
- antigens
33
How do direct ELISA tests work?
- Antibodies bound to the bottom of vessel
- Blood plasma sample added
- Specific antigen binds to antibody in vessel
- Wash out
- Add secondary antibody with enzyme attached
- Binds to antigen bound to AB on vessel
- Wash out
-Add substrate - broken down by enzyme - changes colour
34
What do indirect ELISA test for?
antibodies
35
How do indirect ELISA tests work?
- Antigen bound to bottom of the vessel
- Blood plasma sample added
- Specific antibodies bind to antigens
- Wash out - removes unbound AB
- Secondary antibody with enzyme added
- Binds to primary antibody
- Wash out - removes unbound AB
- Substrate added - reacts with enzyme - colour change
36
What does HIV stand for?
Human Immunodeficiency Virus
37
What does AIDS stand for?
Acquired Immune Deficiency Syndrome
38
What does HIV do?
- Infects and kills T helper cells - host cells
- Low H T cells = no effective immune response
39
What illnesses can you get with HIV?
- Infections of mucus membranes
- Respiratory infections
- Serious infections e.g. TB
- Toxoplasmosis of brain - parasite infection
- Candidiasis of respiratory system - fungal
- Illnesses kill you not HIV
40
What is the structure of HIV?
- RNA - core genetic material
- Reverse transcriptase enzyme - for replication
- Capsid and envelope - made of membrane from host cell
- Attachment protein - stick to host cell
41
How does HIV replicate?
1. Attachment protein binds to receptors on host cell
2. Capsid released into cell - releases genetic info
3. Reverse transcriptase makes complimentary DNA from viral RNA
4. Double stranded DNA made & inserted into human DNA
5. Cell enzymes used to make viral proteins from viral DNA found in human DNA
6. Viral proteins assembled into new viruses - bud from cell & go on to infect others
42
How do antibiotics work?
- Kill bacteria by interfering with metabolic reactions - target enzymes and ribosomes
- Only bacteria harmed
43
Why do antibiotics not work on viruses?
- Viruses are acellular and non living
- Found in host cells so cannot be targeted
44
What do antiviral drugs target?
- Enzymes like reverse transcriptase
- Antiretroviral drugs stop HIV replicating
45
How is HIV controlled?
- Reduce spread in a population
- Safe sex
- Don't share needles
- Can be given mother to baby but can be lowered by use of antivirals
