U4A1: 7D THIRD LINE OF DEFENCE

Question 1

part of the immune system

Answer 1

adaptive or specific

Question 2

how are t-helper cells selected?

Answer 2

APCs travel to lymph notes to present foreign antigens on their surface using MHC 2 proteins. these antigens interact with complementary receptors on the surface of T-helper cells, “selecting” it.

Question 3

humoral immunity

Answer 3

involves the destruction of extracellular pathogens by the production + secretion of antibodies. B-lymphocytes

Question 4

stages of humoral immunity

Answer 4

• pathogen interacts with B-cell with complementary antigen. (clonal selection)
• T-helper cell recognises B-cell and secretes cytokines, triggering clonal expansion and differentiation.

1. clonal selection (pathogen interacts with complementary B-cell, selecting it.)
2. clonal expansion (t-helper cell recognises b-cell and secretes cytokines, replicating the b-cell)
3. differentiation (b-cell clones may differentiate into b-memory cells or plasma cells)

Question 5

what do B-cells differentiate into?

Answer 5

• B-memory cells
• plasma cells

Question 6

role of B-memory cells

Answer 6

responsible for providing long-lasting immunological memory of an antigen.

Question 7

role of plasma cells

Answer 7

responsible for the generation and secretion of antibodies during the humoral response.

Question 8

antibody structure

Answer 8

4 polypeptide chains joined by a disulphide bond.
Y shaped, bottom half is ‘constant region’ and top half is ‘variable region’.
antigens bind at the variable region.
antibodies are specific to an antigen.

Question 9

antibody functions

Answer 9

• neutralisation
• agglutination
• immobilisation
• opsonisation
• activation of complement proteins

Question 10

neutralisation of antibodies

Answer 10

antibodies block the sites of pathogens that attack host cells, and block the active sites of toxins.

Question 11

agglutination of antibodies

Answer 11

bind together with antigens on 2 seperate pathogens, forming antigen-antibody complexes, making it easier for phagocytes to recognise the pathogens as foreign.

Question 12

immobilisation of antibodies

Answer 12

restrict the movement of pathogens through the formation of large antigen-antibody complexes.

Question 13

opsonisation of antibodies

Answer 13

bind to pathogen’s surface to make phagocytosis easier.

Question 14

activation of complement proteins of antibodies

Answer 14

antibodies attach to the surface of pathogens and facilitate the actions of complement proteins, including forming membrane attack complexes.

Question 15

cell-mediated immunity

Answer 15

involves the destruction of infected or abnormal cells via the clonal selection of a cytotoxic-T cell.

Question 16

stages of cell-mediated immunity

Answer 16

• pathogen interacts with T-cell with complementary antigen. (clonal selection)
• T-helper cell recognises T-cell and secretes cytokines, triggering clonal expansion and differentiation.

Question 17

what do T-cells differentiate into?

Answer 17

• T-memory cells
• cytotoxic T cells

Question 17

role of T-memory cells

Answer 17

responsible for providing long-lasting immunological memory of an antigen.

Question 18

role of cytotoxic T cells

Answer 18

when it finds an abnormal cell presenting complementary foreign antigens on its MHC I marker, it binds to it. chemicals are secreted to induce apoptosis.

Question 19

how do B-memory cells contribute to immunological memory?

Answer 19

rapidly dividing and forming new antibody-producing plasma cells when they encounter an antigen that matches their receptor.

Question 20

how do T-cells contribute to immunological memory?

Answer 20

rapidly grow into T-helper cells and cytotoxic-T cells upon stimulation by an APC presenting a previously encountered antigen.

Question 21

advantages of immunological memory

Answer 21

creation of a more rapid and effective immune response upon re-infection, as antibodies and cytotoxic T cells are produced more rapidly to kill infected cells.