5.3->5.5

Question 1

antigen

Answer 1

any part of organism or substance that is recognised as non-self by immune system and stimulates an immune response

usually proteins on csm or cell walls of invading cells

triggers production of antibody

Question 2

lymphocytes

Answer 2

white blood cell
produced by stem cells in bone marrow

Question 3

B-lymphocytes

Answer 3

mature in bone marrow
humoral immunity- involves antibodies that are presented in bodily fluids(humor) e.g. blood plasma

Question 4

T-lymphocytes

Answer 4

mature in thymus gland
cell-mediated immunity- involved body cells

Question 5

4 reasons t-lymphs can distinguish invader cells from normal cells

Answer 5

1. phagocytes that have engulfed and hydrolysed pathogen present some of pathogens antigens on own csm
2. body cells invaded by virus present some viral antigens on own csm
3. transplanted cells from individuals of same species have different antigens on own csm
4. cancer cells are different from normal and present antigens on csm

Question 6

cell-mediated immunity

Answer 6

t-lymphs only respond to antigens presented on a body cell(cellular response)

Question 7

Response of T-lymph to infection

Answer 7

1. pathogens invade body cell or are take in by phagocytes
2. phagocyte places antigen from pathogen on its own csm
3. receptors on specific helper t cell fit excactly onto antigens
4. attachment activates t cell to divide rapidly by mitosis and from clone of genetically identical cells
5. cloned t cells
   - develop into memory cells that enable rapid response to future infections by same pathogen
   - stimulate phagoctes to engulf pathogens by phagocytosis
   - stimulate b cells to divide and secrete antibody
   - activate cytotoxic t cells

Question 8

cytotoxic t cells

Answer 8

kill abnormal cells and body cells infected by pathogens
produce protein perforin that makes holes in csm
cell membrane becomes freely permeable to all substances and cell dies(prevents virus living inc ell from multiplying)

Question 9

humoral immunity

Answer 9

1. pathogen enters the blood or tissue fluid
2. will be a b-cell(out of 10 mill) that has antibody on surface whose shape is complementary so they attach
3. surface antigen enters b cell by endocytosis and gets presented on surface
4. t helper cell binds to processed antigen on b cell
5. b cell is stimulated to divide via mitosis to form clones(clonal selection)- primary immune response
6. cloned plasma cells produce and secrete specific antibody that fit antigen on pathogens surface
7. antibody attached to antigens on pathogen and destroys them
8. b cells develop into memory cells

Question 10

type of clone cells

Answer 10

plasma cells
memory cells

Question 11

plasma cells

Answer 11

secrete antibodies into blood plasma to destroy antigen
survive for few days, but can make approx 2000 antibodies per second

Question 12

memory cells

Answer 12

secondary immune response- long term immunity
circulate in blood and tissue fluid
when encounter same antigen later, they divide rapidly, develop into plasma cells and more memory cells

Question 13

antibodies

Answer 13

proteins with specific binding sites synthesised by b cells

reacts with complementary antigen on surface of non-self material by binding to form antigen-antibody complex

Question 14

structure of anitbody

Answer 14

four polypeptide chains
- heavy chains(long pair)
- light chains(shorter)

2 binding sites is variable region
- different on every antigen
- sequence of amino acids that form specific 3d shape

rest is constant region
- binds to receptors on cells

Question 15

two ways antibodies assist antigen destruction

Answer 15

1. cause agglutination of bacterial cells- clumps of bacterial cells are formed, making it easier for phagocytes to locate as they are less spread throughout body
2. serve as markers that stimulate phagocytes to engulf bacterial cells to which they are attached

Question 16

pathogens antigens

Answer 16

each pathogen has hundreds of different antigens on surafce
each antigen will induce b cells to multiply and form clones, each producing different antibodies

Question 17

monoclonal antibodies

Answer 17

antibodies that can be isolated and cloned
used to target specific substances and cells
e.g. herceptin treats breast cancer

Question 18

direct monoclonal antibody therapy

Answer 18

1. monoclonal antibodies are produced that are specific to antibodies on cancer cells
2. antibodies are given to patient and attach themselves to receptors on cancer cells
3. attach to surface of cancer cells and block chemical signals that stimulate uncontrolled growth
4. not toxic and highly specific so have few side effects

Question 19

indirect monoclonal antibody therapy

Answer 19

attaching radioactive or cytotoxic drug(kills cells) to monoclonal antibody

used in smaller doses
-cheaper and reduces side effects

Question 20

production of monoclonal antibodies

Answer 20

1. mouse is exposed to non-self material against which an antibody is required
2. b cells in mouse produce mixture of anitbodies, which are extracted from the spleen
3. b cells are mixed with cells that dive rapidly outside body e.g. cancer
4. detergent is added to mixture to break down cs, of both type of cells so they fuse to produce hybridoma cells
5. hyridoma cells separate under microscope and each cell is cultured to form a clone(each clone is tested to see if it produces required antibody)
6. any clone producing required antibody is grown on large scale and antibodies are extracted from growth medium
7. monoclonal antibodies are modified to make like humans(humanisation)

Question 21

ethics of monoclonal antibodies

Answer 21

1. induces cancer in mice for production
2. testing of new monoclonal antibody drugs present certain dangers(e.g. one trial caused organ failure in 6 volunteers)
3. death associated with treatment
4. must have informed consent- know risk and benefits

Question 22

medical diagnosis

Answer 22

measures level of substances in blood that are associated with different illness

used for influenza, hepatitis and chlamydia

Question 23

pregnancy test

Answer 23

placenta produces hCG hormone
of hCG is present in urine, monoclonal antibodies linked to coloured particles bind to the antibodies
hCH antibody-colour complex move along strip until trapped by different antibody, creating a coloured line