the immune system (immune response)

Question 1

what is an antigen?

Answer 1

protein that can generate an immune response

Question 2

what are antigens used by the immune system to identify?

Answer 2

pathogens
abnormal body cells, eg cancer cells
toxins
cells from other individuals of the same species eg,organ transplants

Question 3

what is a pathogen?

Answer 3

organism that causes disease

Question 4

what are the 4 stages of the immune response?

Answer 4

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

Question 5

what happens in phagocytosis?

Answer 5

phagocyte recognises foreign antigens on a pathogen
cytoplasm engulfs the pathogen
phagocyte contained in a phagocytic vacuole
lysosome fuses with the phagocytic vacuole
lysozymes break down the pathogen
phagocyte presents the pathogen’s antigen on its surface to activate other immune cells

Question 6

what happens when phagocytes activate T cells?

Answer 6

helper T cells release chemical signals that activate/stimulate phagocytes
cytotoxic T cells kill abnormal and foreign cells
activate B cells which secrete antibodies

Question 7

what is a T cell?

Answer 7

type of white blood cell with receptors on its surface that bind to the complementary antigens presented by phagocytes

Question 8

what is a B cell?

Answer 8

type of white blood cell, covered with antibodies

Question 9

what is an antibody?

Answer 9

protein that binds antigens

Question 10

what happens when B cells meet an antigen?

Answer 10

when the antibody on a B cell surface meets a complementary antigen, it binds to it
this activates the B cell (clonal selection)
activated B cell divides into plasma cells

Question 11

what are plasma cells?

Answer 11

cell that are clones of B cells

Question 12

what do plasma cells do?

Answer 12

secrete monoclonal antibodies, which are specific to the antigen

Question 13

what happens when antibodies bind to antigens on the surface of the pathogen?

Answer 13

forms an antigen-antibody complex

Question 14

why does an antibody have two binding sites?

Answer 14

can bind to 2 pathogens at the same time
pathogens become clumped together=agglutination
phagocytes bind to antibodies and phagocytose many pathogens at once

Question 15

why is an antibody specific?

Answer 15

has variable regions which make up the antigen binding sites
have a unique tertiary structure

Question 16

what is the cellular immune response?

Answer 16

T cells and other immune system cells that they interact with

Question 17

what is the humoral immune response?

Answer 17

B cells, clonal selection and the production of monoclonal antibodies

Question 18

what is the primary immune response?

Answer 18

when an antigen enters the body for the first time

Question 19

what happens in the primary immune response?

Answer 19

slow as there aren’t many B cells
infected person shows symptoms whilst producing the antibody
after exposure, T and B cells produce memory cells so the person is immune

Question 20

what is the role of a memory T cell?

Answer 20

remember the specific antigen and will recognise if it enters the body again

Question 21

what is the role of a memory B cell?

Answer 21

records the specific antibodies needed to bind the antigen

Question 22

what is the secondary immune response?

Answer 22

when the same pathogen happens again

Question 23

what happens in the secondary immune response?

Answer 23

clonal selection occurs faster
memory B cells activated and divide into plasma cells
memory T cells are activated and divide into the correct type of T cells
rid of pathogen before symptoms