2.4 Immunity

Question 1

what is a specific response

Answer 1

slower and specific to each pathogen

Question 2

what is a non specific response

Answer 2

response is same for every pathogen

Question 3

examples of non specific responses

Answer 3

phagocytosis
first line defences

Question 4

examples of specific responses

Answer 4

cell mediated response (T CELLS)
humoral response (B CELLS)

Question 5

what response does t cells involve

Answer 5

cell mediated

Question 6

what response does b cells involve

Answer 6

humoral

Question 7

what is a pathogen

Answer 7

organisms that cause disease
- contain antigens on the surface so they can be identified and destroyed

Question 8

what is an antigen

Answer 8

proteins that can generate an immune response when detected by the body

Question 9

process of phagocytosis

Answer 9

1. phagocyte is attracted to pathogen by its chemical products
2. phagocyte and pathogen fuse together
3. phagocyte engulfs pathogen forming a phagosome
4. lysosomes then fuse with phagosome
5. lysozymes hydrolyse bacteria
6. products of hydrolysis are absorbed by phagocyte
7. phagocyte becomes an antigen presenting cell

Question 10

what is antigenic variation

Answer 10

process where a pathogen alters the shape of proteins on its surface and avoids a host response as memory cells no longer recognise the antigens

Question 11

explain the cell mediated response

Answer 11

• macrophage ingests antigens and presents them to a T cell which divides them into 4 clones
• (killer, cytotoxic, memory and suppressor)

Question 12

explain the humoral responses

Answer 12

1. pathogen present in blood with a specific antigen
2. complimentary antibody on B cell surface binds with antigen, takes it in and presents antigens on it’s surface
3. helper T cell activates B cell
4. B cells divide by mitosis (clonal expansion) to produce memory cells and plasma cells

Question 13

what are the 4 cells T lymphocytes divide into (cell mediated response)

Answer 13

• helper T cells
• cytotoxic T cells
• memory T cells
• suppressor T cells

Question 14

what is the role of memory B cells (humoral response)

Answer 14

remain in blood and will rapidly divide into plasma cells if antigen returns in future

Question 15

what is the role of plasma B cells

Answer 15

release antibodies

Question 16

what do T helper cells do

Answer 16

release cytokines that T cells, B cells and phagocytes respond to

Question 17

what do cytotoxic T cells do

Answer 17

causes lysis of target cells and will destroy virus infected or cancer cells

Question 18

what do antibodies do

Answer 18

form an antigen antibody complex which serve as markers for phagocytes to destroy attached cells
- have two binding sites so can clump cells together to make it easier for phagocytes to find - agglutination

Question 19

what is an antibody

Answer 19

made of four polypeptide chains and are complimentary to only one antigen
- form an antigen antibody complex

Question 20

what is active immunity

Answer 20

production of antibodies from the immune system in the presence of an antigen

Question 21

what is passive immunity

Answer 21

introduction of antibodies from another person or animal

Question 22

what is natural passive immunity

Answer 22

antibodies come from mother (through placenta or breast milk)

Question 23

what is natural active immunity

Answer 23

being exposed to the antigen

Question 24

what is active artificial immunity

Answer 24

acquired through a vaccine which stimulates immune system to produce antibodies

Question 25

what is passive artificial immunity

Answer 25

antibodies are injected into the body

Question 26

what is a vaccine

Answer 26

- dead or inactive form of a pathogen injected into the body to produce an immune response

Question 27

what is herd immunity

Answer 27

the idea that if enough people within a population are injected the pathogen wont be able to be passed between hosts

Question 28

why are vaccines not always useful

Answer 28

antigens on the surface of the pathogen can change so immunity is removed

Question 29

ethical issues with vaccines

Answer 29

- testing could be done on animals - expensive - people should have an option - must be tested on humans to detect toxicicity

Question 30

what is monoclonal antibodies

Answer 30

many clones of a single antibody

Question 31

structure of HIV

Answer 31

- lipid envelope embedded with attachment proteins - genetic material and reverse transcriptase ( DNA > RNA ) found inside a protein capsid

Question 32

how is HIV replicated

Answer 32

- binds to CD4 which is found on helper T cells - capsid fuses with cell surface membrane - RNA and reverse transcriptase enters the cell - RNA is converted to DNA by reverse transcriptase, this moves into the nucleus - HIV components are produced by the cell

Question 33

how does an ELISA test work?

Answer 33

- enzyme attached to antibodies - when reacts with certain substrate, a colour product is formed - colour change shows antigen is present in the sample

Question 34

why are antibiotics ineffective against viruses and HIV

Answer 34

- antibiotics work by preventing bacteria from forming cell walls so the bacteria can’t control the entry and exit of water so the cell bursts - viruses don’t have a cell wall so are unaffected

Question 35

how is HIV treated

Answer 35

antiretroviral drugs

Question 36

how do antiretroviral drugs work

Answer 36

keep the levels of HIV in the blood stream very low, reducing the impact on the hosts immune system.