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Biology > Topic 2C: Cells and the Immune System > Flashcards

Topic 2C: Cells and the Immune System Flashcards

1
Q

What is an antigen?

A
  • Usually a protein / glycoprotein
  • Non-self –> generate immune response
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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
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3
Q

How does phagocytosis occur?

A
  1. Phagocyte recognises non-self antigens
  2. Phagocyte engulfs pathogen - cytoplasm moves around it
  3. Pathogen contained in phagocytic vacuole
  4. Lysosome fuses releasing lysozymes to hydrolyse and break down pathogen
  5. Antigens can be stuck on surface to be an antigen presenting cell and activate immune cells
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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
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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
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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
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7
Q

How do antibodies help immune response?

A
  • 2 binding sites so can clump pathogens
    –> agglutination
  • Easier for phagocytosis
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8
Q

What is cellular response?

A
  • T cells and other immune system cells they interact with –> phagocytes
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9
Q

What is humoral response?

A
  • B cells, clonal selection, antibody production
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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
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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
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12
Q

What is active immunity?

A
  • When the immune system makes it’s own antibodies from an antigen stimulus
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13
Q

What is natural active immunity?

A
  • Immunity comes from catching an illness
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14
Q

What is artificial active immunity?

A
  • Immunity comes from a vaccine
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15
Q

What is passive immunity?

A
  • Given antibodies from another organism
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16
Q

What is natural passive immunity?

A
  • Baby immune due to mother’s antibodies from placenta and milk
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17
Q

What is artificial passive immunity?

A
  • Injected with antibodies from someone else e.g. for tetanus
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18
Q

What are the features of active immunity?

A
  • Longer lasting
  • Memory cells produced
  • Need exposure to antigen
  • Takes longer to form protection
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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
Q

What are ethics of vaccination?

A
  • 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
Q

What is herd immunity?

A
  • Susceptible people protected by the immunity of others in the population –> disrupts transmission
27
Q

What is a monoclonal antibody?

A
  • Produced from genetically identical B cells
  • Complimentary to antigen - unique tertiary structure
28
Q

How can antibodies treat cancers?

A
  • Cancer cells have tumour markers
  • Monoclonals can be specific and bind to these carrying an anti cancer drug
29
Q

How is this treatment good?

A
  • Only targets cancer cells so there are fewer side effects - normal body cells unaffected
30
Q

How do pregnancy tests work?

A
  • 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
Q

What do ELISA tests do?

A
  • 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
Q

What do direct ELISA test for?

A
  • antigens
33
Q

How do direct ELISA tests work?

A
  • 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
Q

What do indirect ELISA test for?

A

antibodies

35
Q

How do indirect ELISA tests work?

A
  • 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
Q

What does HIV stand for?

A

Human Immunodeficiency Virus

37
Q

What does AIDS stand for?

A

Acquired Immune Deficiency Syndrome

38
Q

What does HIV do?

A
  • Infects and kills T helper cells - host cells
  • Low H T cells = no effective immune response
39
Q

What illnesses can you get with HIV?

A
  • 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
Q

What is the structure of HIV?

A
  • 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
Q

How does HIV replicate?

A
  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
Q

How do antibiotics work?

A
  • Kill bacteria by interfering with metabolic reactions - target enzymes and ribosomes
  • Only bacteria harmed
43
Q

Why do antibiotics not work on viruses?

A
  • Viruses are acellular and non living
  • Found in host cells so cannot be targeted
44
Q

What do antiviral drugs target?

A
  • Enzymes like reverse transcriptase
  • Antiretroviral drugs stop HIV replicating
45
Q

How is HIV controlled?

A
  • 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

Biology (11 decks)

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