cell recognition and the immune system

Question 1

what is an antigen?

Answer 1

a foreign protein that stimulates an immune response

Question 2

what types of cells do antigens enable the immune system to identify?(4)

Answer 2

pathogens

cells from other organisms of the same species

abnormal body cells

toxins.

Question 3

what is antigenic variation and what effect does it have on disease prevention?

Answer 3

when mutations cause antigens to alter their tertiary structure
As a result, memory cells do not detect the altered antigens and are no longer effective against the pathogen.

Question 4

what type of white blood cell is involved in non-specific response?

Answer 4

phagocyte

Question 5

what are the 4 stages of phagocytosis?

Answer 5

phagocyte engulfs the pathogen forming a phagosome

lysosomes containing lysozymes fuse with the phagosome

the lysozymes hydrolyse the pathogen

the antigens are presented on the cell surface membrane.

Question 6

what lymphocytes are involved in the cell mediated response and where do they mature?

Answer 6

T-lymphocytes mature in the thymus gland

Question 7

how do helper T-cells begin a response to infection?

Answer 7

receptors on a specific helper T-cell binds to an APC

this activates the T-cell to begin dividing by clonal selection

Question 8

what can cloned T-cells do?(4)

Answer 8

develop into memory cells

stimulate phagocytosis

stimulate B-cells to divide and secrete antibodies

activate cytotoxic t-cells

Question 9

how do cytotoxic T-cells kill pathogens?

Answer 9

they produce a protein called perforin

perforin creates holes in the cell membrane, making it freely permeable and thus killing the cell

Question 10

what lymphocytes are involved in the humoral response and where do they mature?

Answer 10

B-lymphocytes mature in the bone marrow

Question 11

describe the humoral response(4)

Answer 11

helper T-cell with complementary receptor binds to antigen on an APC

stimulates a specific B cell with complementary antibody on its surface

this stimulates the b-cell to divide and produce many plasma cells that all produce the same antibody

or produce memory cells which will be able to recognise and more rapidly destroy the same pathogen in the future.

Question 12

what are antibodies?

Answer 12

a protein that is produced by a plasma b-cell

Question 13

describe the structure of an antibody(2)

Answer 13

have a quaternary structure with 2 heavy polypeptide chains and 2 light polypeptide chains joined by disulfide bridges

each antibody has 2 identical antigen binding sites that have a specific tertiary structure that is complementary to a specific antigen

Question 14

what 2 ways can antibodies kill a pathogen?

Answer 14

agglutination
acting as a marker for phagocytes

Question 15

how does agglutination help destroy pathogens?

Answer 15

each antibody can bind to 2 antigens and clump them together making it easier to engulf or deactivating viruses

Question 16

how does acting as a marker help destroy pathogens?

Answer 16

antibody binds to the pathogens antigen and the constant region is then recognised by a phagocyte

Question 17

what is a monoclonal antibody

Answer 17

​Identical antibodies that have been produced by a single b-cell that has been cloned

Question 18

what are the 5 steps of an (direct) ELISA test?

Answer 18

specific monoclonal antibody is attached to plate

sample is added, if there are antigens with a complementary shape they will bind to the antibodies

rinse plate to get rid of unbound antigens

add a second MAB that is attached to an enzyme, rinse again

add substrate for the enzyme

Question 19

what is a vaccine?

Answer 19

introduction of dead or inactive pathogens with specific antigens to produce an immune response

Question 20

how do vaccines protect against disease?

Answer 20

vaccine contains dead antigen

memory cells made on first encounter

on second exposure, memory cells recognise antigen and produce more antibodies more rapidly

antibodies destroy pathogens before they cause harm

Question 21

what is passive immunity?(2)

Answer 21

introduction of antibodies from an outside source

it is short term because the antibodies will eventually be broken down

Question 22

what is active immunity?(2)

Answer 22

when own immune system is stimulated to produce antibodies

it is long term because memory cells are produced

Question 23

what is herd immunity?

Answer 23

when a sufficiently large proportion of the population has been vaccinated against a disease, making it difficult for the disease to spread.

Question 24

name 5 structures of a HIV

Answer 24

lipid envelope
attachment proteins
reverse transcriptase
capsid
RNA

Question 25

how does HIV lead to AIDS?

Answer 25

HIV attacks T-cells so immune system becomes weaker

this means less antibodies are produced as less b-cells are activated

Question 26

how does HIV replicate?(6)

Answer 26

1. attachment proteins on the HIV bind to CD4 receptors on a helper T-cell
2. RNA and reverse transcriptase is inserted into the cell
   3.Reverse transcriptase converts RNA to DNA
3. viral integrase inserts DNA into host cells DNA
   5.viral mRNA is transcribed at ribosomes, forming viral proteins
4. Virus is assembles and released from the cell

Question 27

what are 4 uses of monoclonal antibodies?

Answer 27

treating cancer
research
medical diagnosis
drug testing

Question 28

how can MABs be used for treating cancer?

Answer 28

a radioactive cytotoxic drug can be attached to an antibody which will then deliver it to the cancer cells with the complementary antigens

Question 29

what are some ethical issues to do with vaccines?

Answer 29

production often involves animals

may have side effects

some people may not want to have a vaccine

Question 30

what are ethical issues of using MABs?

Answer 30

production involves mice

some risks of treatment failing

clinical tests may be risky