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2c (immune system) Flashcards

cells and the immune system

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1
Q

What is an antigen?

A

A molecule (protein) found on the surface of cells that can generate an immune response when detected by the body.

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2
Q

4 examples of antigen presenting cells

A

phagocyte that engulfed a pathogen, body cell invaded by a virus, cancerous cell, foreign transplanted material

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3
Q

What is a pathogen?

A

A microrganism that causes disease

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4
Q

What are the four main stages of the immune response?

A

Phagocytes engulf pathogens
phagocytes activate T cells
T cells activate B cells which divide into plasma cells
Plasma cells make more antibodies to a specific antigen

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5
Q

What is the first cell in the immune system to respond to antigens?

A

Phagocytes

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6
Q

Describe phagocytosis

A

Phagocyte recognises foreign antigen
Cytoplasm of phagocyte moves round pathogen engulfing it
Pathogen is now contained in phagocytic vacuole in the cytoplasm of the phagocyte
A lysosome fuses with the phagocytic vacuole and lysozymes digest pathogen
Phagocyte present pathogens antigens by sticking them on its surface to activate other immune system cells

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7
Q

What is a T cell/ T lymphocyte? where are they produced/ matured?

A

Type of white blood cell with receptor proteins on surface which bind to complimentary antigens presented to it by phagocytes which activate it
produced in bone marrow and matured in thalamus gland

cell mediated response

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8
Q

What is a T helper cell

A

T cell that releases chemical signals (cytokines) that activate and stimulate phagocytes and cytotoxic T cells. Also activate B cells which secrete antibodies

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9
Q

What is a cytotoxic T cell?
what happens when theyre activated?

A

T cell that kills abnormal and foreign cells
once activated, proliferate to make clones specific to 1 antigen, some differentiate into long lived memory t cells
most mature to attack and destroy infected cells

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10
Q

how do cytotoxic t cells destroy cells?

A

secrete perforin which forms pore in membrane of target cell
secret granzyme which enters cell through pores and activates enzymes in cell to cause cell death
pores also mean contents of cell leaks out causing death

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11
Q

What is the role of B cells? where are they produced/ matured?

A

Antibody on its surface binds to complimentary antigen
This and substances released from helper T cells activated B cells (clonal selection)
Activated B cell divides into plasma cells
produced in bone marrow and matured in lymph nodes

humoral response

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12
Q

What are plasma cells?

A

Clones of B cells that secrete antibodies specific to antigen
Monoclonal antibodies
Bind to antigens on surface of pathogen

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13
Q

Structure of antibodies

A

Proteins
Specificity of antibody depends on variable regions which form antigen binding sites
Variable region with unique tertiary structure complimentary to specific antigen
Same constant region
2 light 2 heavy???

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14
Q

function of antibodies

A

coat pathogen so easier for phagocytes to engulf
coat pathogen to prevent entering host
bind to and neutralise toxins produced by pathogens

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15
Q

What is agglutination?

A

antibodies have 2 binding sites so can bind to 2 antigens at a time. results in the clumping together of cells or particles which assists phagocytosis

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16
Q

What is cellular immune response?

A

T cells and other immune system cells they interact with
Eg phagocytes

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17
Q

What is humoral response?

A

B cells, clonal selection and production of monoclonal antibodies from the humoral response

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18
Q

What is a primary immune response?

A

Antigen first activates immune system
Slow as not many b cells to make antibodies
Eventually enough antibody made to overcome infection but person shows symptoms
T and b cells produce memory cells which stay in body. Memory t recognise specific antigen and memory b record specific antibodies needed
Person now immune

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19
Q

What does it mean to be immune?

A

have memory B cells which can divide and differentiate into plasma cells and quickly destroy pathogens before you get symptoms

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20
Q

What is the secondary immune response

A

Same pathogen enters second time and immune system can produce quicker stronger immune response
Clonal selection happens quicker
Memory b cells activated and divide into plasma cells that produce antibodies
Memory t cells activated and divide into correct T cell to kill cell carrying antigen
Gets rid of pathogen before show symptoms (immune)

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21
Q

what is a vaccine?
what does it contain?

A

dead or inactive part of a pathogen that stimulates an immune response
contains antigens that cause body to produce memory cells wo causing disease so immune wo symptoms

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22
Q

what is herd immunity?

A

more people with vaccine means less people with disease.
vaccinated people mean it is hard to spread even to those not vaccinated so helps people who cant get vaccine

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23
Q

different types of antigen in a vaccine?

A

free or attached, dead (cant replicate) or attenuated (cant cause disease but still replicate and give strongest immune response cant give to people who are immunosuppressed)

24
Q

disadvantage of taking vaccine orally

A

could be broken down by enzymes in gut or molecules may be too large to be absorbed into blood

25
Q

why may a booster vaccine be needed?

A

antigen variation
and to make sure memory cells are produced
or if killed vaccine was used (produces weaker immune response)

26
Q

what is antigenic variation?

A

different antigens formed due to changes in the pathogens genes
immune system cant recognise even if already been infected w that pathogen so have to start from scratch
hard to develop vaccines and have to keep getting new ones

27
Q

how does antigenic variation cause people to keep getting the flu

A

antigens on surface change forming new strains
memory cells from old vaccine dont recognise- immunologically distinct
new vaccines have to be created

28
Q

antigenic drift vs antigenic shift

A

antigenic drift- small changes as virus replicates so still similar so immune system may still recognise it
antigenic shift- abrupt, major change resulting in subtypes of the virus, no protection

29
Q

how vaccines make us immune 5 marks

A

vaccines contain antigens which bind to surface protein receptor of T helper cells?
now activated (by t cells and cytokines) b cells divide by mitosis producing clones called plasma cells
these release antibodies
some b cells become memory cells
these produce antibodies faster

30
Q

what is active immunity? What are the 2 types?

A

immune system makes own antibodies after stimulated by antigen
natural- immune after catching disease
artificial- immune after vaccine

31
Q

what is passive immunity?
what are the 2 types?

A

immune after being given antibodies by different organism
natural- from antibodies in breast milk/ from placenta
artificial- injected with someone else’s eg from blood donations

32
Q

contrast active and passive immunity

A

active- exposure to antigen passive- not
active- takes time to be immune passive- immediate
active- memory cells produced passive-not
active- long term protection passive- short term as antibodies given are broken down

33
Q

what is the difference between HIV and AIDS?

A

HIV is a virus affecting immune system that leads to AIDS
AIDS is a condition where immune system deteriorates and fails making someone more vulnerable to other infections

34
Q

How does HIV lead to AIDS?

A

HIV kills T helper cells (the host cells for HIV)
T helper cells send chem signals that activate phagocytes, cytotoxic t cells and cells so without them, body cant produce effective immune response
AIDS is developed when t cells decrease to a critically low level

35
Q

what to HIV and AIDS stand for?

A

human immunodeficiency virus
acquired immune deficiency syndrome

36
Q

what is the structure of HIV?

A

core of RNA and some proteins eg reverse transcriptase
capsid
envelope made of membrane of host cell
attachment proteins that help HIV attach to host

37
Q

how does HIV replicate?

A

attachment protein attaches to receptor molecule on cell membrane of t helper cell
capsid released into cell where is uncoats and releases RNA into cells cytoplasm
inside cell, reverse transcriptase is used to make complimentary strand of DNA from viral RNA template
from this, double straded DNA is inserted into human DNA
host cell enzymes used to make viral proteins from viral DNA in humans DNA
viral proteins assembled into new viruses which bud from cell and go on to infect other cells

38
Q

3 stages of HIV

A

active infection- lots of replication and flu like symptoms
clinical latency- reproduces at low levels, may be asymptomatic, with treatment, lasts decades, wo, 10 years
AIDS- CD4 cells fall below 200 cells/mm2
wo treatment, survive around 3 years

39
Q

3 stages of AIDS

A

initial symptoms- minor infections of mucous membranes and recurring respiratory infections
progressive- immune system cells decrease further, more susceptible to serious infections eg severe bacterial infections and tb
late- very low no of immune system cells, can develop toxoplasmosis of the brain, candidiasis of the respiratory system and meningitis
it is these that kill AIDS patients not HIV itself

40
Q

why cant antibiotics be used for AIDS?

A

antibiotics kill bacteria by interfering with their enzymes and ribosomes which are diff to human ones so human cells are not affected
viruses dont have own enzymes and ribosomes to replicate so use humans so antibiotics cant inhibit them

41
Q

what are reverse transcriptase inhibitors?

A

antiviral drugs that inhibit reverse transcriptase as it is a virus specific enzyme so humans dont use it and arent affected
HIV uses it to replicate

42
Q

no cure for HIV but hat can we do?

A

antiviral drugs can slow down progression
best to control spread
spread via sharing infected bodily fluids (unprotected sex, sharing needles, and from mother to fetus)
not all babies from HIV positive mothers are born with HIV and can reduce chance by taking antiviral drugs during pregnancy

43
Q

what is proliferation of t helper cells?

A

proliferate once activated, form clone of itself specific to same antigen, some become long lived memory t cells
most mature to produce cytokines to help w immediate cell mediated response

44
Q

what are the 2 types of specific response?

A

cell mediated
t cells
secrete antibodies that remain on the surface of the cell
humoral
b cells
release antibodies

45
Q

what are monoclonal antibodies?

A

antibodies with the same tertiary structure
antibodies produced from plasma cells that have been isolated and cloned

46
Q

uses of monoclonal antibodies

A

target medication at particular cell types eg cancer drugs at cancer cells
medical diagnosis eg pregnancy tests and identifying cancel cells
ELISA testing

47
Q

how do monoclonal antibodies target drugs to cancer cells?

A

cancer cells antigens are tumour markers- not on normal body cells
attach cancer drug to antibody and will bind to tumour markers accumulating only where the cancer cells are
so, less side effects and cheaper

48
Q

how does a pregnancy test work?

A

application area contains antibodies complimentary to hCG, bound to coloured beads
urine applied, any hCG binds to antibodies forming antigen- antibody complex. urine moves up carrying beads with it
test strip has immobilised antibodies to hCG so is present, test strip turns blue as immobilised antibodies bind to hCG
not present, beads pass through test area
control window contains immobilised antibodies specific to mobile antibodies from reaction zone

49
Q

What is an ELISA test?

A

enzyme-linked immunosorbent assay
allows you to see if patient has antibodies to a certain antigen or an antigen to a certain antibody

50
Q

describe a direct ELISA test

A

testing for presence of antigen in a sample
antigens from patient bound to inside of a well
antibody complimentary to antigen and with an enzyme attached is added
the well is washed to remove unbound antibodies
add substrate and if enzyme reacts, antibody has bound not washed away so antigen is present

51
Q

describe indirect ELISA test for antibodies
eg HIV

A

antigens bound to bottom of reaction vessel and blood plasma sample added
any antibodies in blood specific to antigen will bind- these are primary antibodies
any unbound are washed out
secondary antibodies with enzymes attached are added and bind to primary then wash out again (to avoid false positive)
substrate added and reacts w enzyme. if secondary antibodies present, coloured product forms

52
Q

describe indirect ELISA test for antigens
eg PSA (prostate specific antigens)

A

antibodies bound to bottom of reaction vessel and blood plasma sample added
any antigens in blood specific to antibody will bind
any unbound are washed out
antibodies with enzymes attached are added and bind to antigens then wash out again (to avoid false positive)
substrate added and reacts w enzyme. if secondary antibodies present, coloured product forms

53
Q

ethical issues of vaccines

A

tested on animals
testing on humans can be risky eg have unprotected sex as think immune from HIV but vaccine may not work
some dont want it but herd immunity so okay but could be unfair
who receives vaccine first

54
Q

ethical issues of monoclonal antibodies

A

animals used to produce cells from which they are produced

55
Q

why might a mutation make no difference to the polypeptide structure

A
  1. Triplets code for same amino acid
  2. Occurs in introns /non-coding sequence

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