- alevel biology > Immunity > Flashcards

Immunity Flashcards

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1
Q

what are the defence mechanisms?

A

non specific - immediate, same for all pathogens
specific - slower, specific to pathogen

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2
Q

what type of response is phagocytosis?

A

non specific

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3
Q

what type of response is humoral response?

A

specific

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4
Q

What type of response is cell-mediated response?

A

specific

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5
Q

Describe how phagocytic white blood cells destroy bacteria

A

phagocyte attracted to pathogen by chemicals. move down chemical gradient
cell surface membrane receptors attach to antigens on surface of pathogen
phagosome formed by engulfing pathogen
lysosomes fuse with phagosome and release lysozymes, hydrolyse pathogen
soluble products absorbed into cytoplasm or expelled out of cell

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6
Q

How do lymphocytes recognise own cells?

A

have antigen receptors to distinguish self from foreign cells (non-self)

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7
Q

What are antigens?

A

molecules which are recognised as non-self by the immune system: identify cell type
proteins or glycoproteins

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8
Q

why might auto-immune disorders occur?

A

body doesn’t recognise self-antigens

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9
Q

give two structures a bacterial cell may have that a white blood cell does not have

A
  1. Cell wall;
  2. Capsule / slime layer;
  3. Circular DNA;
  4. Naked DNA / DNA without histones;
  5. Flagellum;
  6. Plasmid;
  7. Pilus;
  8. 70s / smaller ribosomes;
  9. Mesosome
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10
Q

Phagocytes and lysosomes are involves in destroying microorganisms. Describe how

A

Phagocytes engulf pathogens/microorganisms;
Enclosed in a vacuole / vesicle/ phagosome;
Lysosomes have enzymes;
That digest/hydrolyse molecules/proteins/lipids/microorganism;

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11
Q

Give two ways in which pathogens can cause disease when they enter the body of their host

A

damage host cells
produce toxins

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12
Q

What are the roles of lymphocytes?

A

have a large nucleus (not lobed) to produce lots of antibodies

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13
Q

why are lymphocytes involved in the specific immune response?

A

only activated by one particular antigen

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14
Q

what are B lymphocytes?

A

mature in bone marrow and migrate to lymph nodes

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15
Q

what are T lymphocytes?

A

migrate to thymus gland for period of maturation before migrating to lymph nodes

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16
Q

What are mature B cells?

A

plasma cells:
produce antibodies - destroy pathogen or neutralise toxins

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17
Q

What are the characteristics of plasma cells?

A

specific binding cite
3D protein shape
found on CSM or in plasma of blood

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18
Q

How do lymphocytes respond to infection?

A

millions in body (not made, already exist) increase number of lymphocytes with correct antigen receptor for particular pathogen

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19
Q

How can T lymphocytes distinguish non-self from self?

A

phagocytes present pathogens antigens on own CSM
body cells invaded by virus present viral antigens on own CSM
transplanted cells have different antigens on CSM
cancer cells different from normal body cell present antigens on CSM

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20
Q

what are the key steps in cell mediated response?

A

pathogens invade body cells or taken in by phagocytes
phagocytes display antigens from pathogen on CSM
receptors on T cell fit exactly on antigens
attachment activates T cell to divide rapidly by mitosis - form clone of identical cells

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21
Q

What happen to cloned T cells?

A

develop into T memory cells
T helper cells activate Tc cells
cytotoxic T cell bids to antigen on infected cell
Tc kills abnormal and foreign cells
Th also stimulate B cells which secrete antibodies

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22
Q

What do cytotoxic cells do?

A

bind to infected cell
perforin (protein made) makes holes in CSM
holes mean CSM is freely permeable to all substance and cell dies as result

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23
Q

What is the humoral response?

A

millions of B cells - complementary to millions of pathogens
B cell engulfs and present antigens
B cell meets activated Th cell (cytokines released) - causes it to become activated - clonal selection
B cells differentiate into loads of plasma cells and B memory cells by mitosis - clonal expansion
plasma cells make antibodies
B memory cells differentiate into plasma cells and more B memory cells

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24
Q

What are the structures in an antibody?

A

light chain, heavy chain, constant region, variable regions
disulphide bridges
antigen binding site

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25
how do antibodies trigger pathogen destruction?
agglutination opsonisation neutralisation
26
What is agglutination?
binding of antibodies causes pathogens to clump together - helps prevent spread and makes easier for them to be engulfed by pathogens
27
What is opsonisation?
antibody acts as an opsonin, chemical which makes pathogen more easily recognised by phagocytes
28
what is neutralisation?
neutralise effects of bacterial toxins by binding to them
29
What are the uses of monoclonal antibodies?
They are used in cancer treatment. The a radioactive chemical or a drug can be fixed to the monoclonal antibodies, which then destroys specific cells.
30
Describe how presentation of a virus antigen leads to the secretion of an antibody against this virus antigen
B cells are activated by T cell, b cells differentiate into plasma cells which release antibodies
31
What is an antigen?
Foreign protein on cell surface membrane which stimulates immune response
32
What is an antibody?
protein specific to an antigen which is produced by b cells
33
Why don't you get ill from the same pathogen twice?
B memory cells recognise antigen -> divide into B plasma cells quickly produce lots of antibodies, fast
34
What are the types of vaccines?
dead/live pathogens lab based-antigen mRNA attenuated - weakened pathogen
35
What are the ways of developing immunity?
artificial passive artificial active natural passive natural active
36
what is artificial passive immunity?
artificially produced antibodies injected
37
what is artificial active immunity?
injection of an attenuated pathogen, inducing humoral response most immunisation programmes (dead/weakened)
38
what is natural passive immunity?
antibodies received through body fluid e.g. mother to baby
39
what is natural active immunity?
activity of lymphocytes in response to infection by pathogen
40
Why vaccinate?
decrease general incidence of disease in population
41
Why can't everyone be vaccinated?
weak immune system young/old allergic (egg)
42
What is herd immunity?
occurs when significant proportion of population is vaccinated makes difficult for disease to spread as so few people are vulnerable to it
43
What is HIV?
human immunodeficiency virus
44
What are the structures in HIV?
attachment proteins lipid envelope capsid genetic material (RNA) reverse transcriptase
45
Why can't HIV replicate on their own?
no ribosomes
46
How does HIV replicate?
viral RNA enters the cell viral reverse transcriptase enzymes produce a DNA copy of the viral RNA the DNA copy is inserted into the chromosomes of the cell each time the cell divides it copies the viral DNA HIV proteins are produced from the viral DNA the proteins are used to build new HIV particles thousands of new HIV particles are released, killing the helper T cell the new HIV particles go on to infect other helper T cells
47
How does HIV cause AIDS?
virus gradually reduces number of T helper cells in immune system B cells no longer activated no antibodies produced decreases bodies ability to fight off infections - susceptible to other infections and cancers
48
Why are antibiotics ineffective in treating HIV?
1. viruses rely on host cell for metabolic reactions - don't have own metabolic pathways and cell structure so antibiotics can't disrupt metabolism or protein synthesis 2. protein coat, no murein cell wall 3. often within organism own cell - antibiotics can't reach
49
How is HIV treated?
Antiretroviral therapy: prevent HIV from multiplying - reduces amount of HIV in body (viral load) therefore immune system has time to recover so strong enough to fight off infections
50
Describe how new viruses are produced after HIV has infected a T cell
HIV DNA is inserted into host cell which uses viral DNA to make viral proteins and viral RNA. Host cell makes new virus which break away and bud off from cell
51
What is a monoclonal antibody?
a single antibody isolated and cloned outside of body
52
What are the uses of monoclonal antibodies?
targeted medication medical diagnosis and pregnancy testing
53
What is targeted medication?
direct monoclonal antibody therapy: MCA produced are specific to antigens on cancer cells antibodies given to patient which attach to receptors on cancer cells blocks chemical signals that stimulate uncontrolled growth indirect monoclonal antibody therapy: attaching radioactive or cytotoxic drug to monoclonal antibody - kills
54
How are monoclonal antibodies used in pregnancy test
Pregnant women produce HCG hormone which binds to monoclonal antibodies - produces positive result
55
What is an elisa test?
Enzyme Linked Immunosorbent Assay
56
Describe the role of antibodies in producing a positive result in an ELISA test
antibody binds to antigen, add secondary antibody with conjugated enzyme, secondary antibody attaches to primary antibody, causes colour change when substrate added
57
Why will an antibody only detect a specific antigen?
Antibody has specific binding site which is complementary to antigen. Binding site is affected by amino acid sequence which causes different tertiary structure of binding site. Forms complex between antigen and antibody
58
Why is it necessary to block unoccupied binding sites in microtiter wells?
to prevent non-specific binding of antibodies which can affect results
59
why is it important to have a positive control?
confirms test works and is reliable
60
What could cause a false positive in an ELISA?
non-specific binding of antibodies
61
Why will solution not change colour if person not infected with HIV?
as HIV antibody isn't present so secondary antibody cannot bind
62
what are two purposes of the control well in ELISA?
show only enzyme cause colour change shows washing out wells is effective
63
Why aren't antibiotics used to treat viral infections?
antibiotics disrupt metabolism and viruses are non-living so don't metabolise viruses can hide in cells, antibiotics can'r reach
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