Third line of defence

Question 1

what initiates the third line of defence

Answer 1

the presentation of an antigen with MHC II markers

Question 2

what is the role of dendritic cells/macrophages in the third line of defence

Answer 2

they engulf and digest a pathogen, presenting the antigens of the pathogens on their own MHC II markers, they then travel to the lymph node where they encounter T helper cells

Question 3

T helper cells are aka

Answer 3

T lymphocytes, CD4+ cells

Question 4

when a macrophage/dendritic cell encounters a t helper cell, rarely anything happens, why…

Answer 4

T helper cells all have unique T-cell receptorrs on there surface, rarely anyything happens because the macrophage/dendritic cell and t-helper cell dont have matching antigens

Question 5

what happens when the dendritic cell/macrophage encounters the specific T-helper cells

Answer 5

they bind and the t-helper cell becomes avtivated, causes the naive t-cells to undergo colonal selection and cytokines are released

Question 6

what are the two processes of the third line of defence

Answer 6

humoural response annd cell mediated response

Question 7

cell mediated response

Answer 7

uses T cells to target antigens, effective against intracellular pathogens

Question 8

when a helper t-cell secretes cytokines after binding to the macrophage/dendrites, what does this cause

Answer 8

the cytokines stimulates the helper t-cells to unergo clonal expansion - rapid miotic division (all with the have same receptors as original) and differentiation into cytotoxic t-cells and t memory cells

Question 9

what do the cytotoxic cells do once produced/differentiated

Answer 9

they spread throughout the body and identify self cells in the body that have foreugn antigens rgat fit their t-cell receptors, presented on its MHC I marker, they tthen release a death lignand that induces apoptosis in the infected in the cell

Question 10

humoral immunity

Answer 10

effective against extracellular pathogens, neutralising and destroying them

Question 11

structture of B lymphocytes

Answer 11

covered in antibodies (immunoglobulins) and contain MHC II markers

Question 12

where are B lymphocytes found

Answer 12

reside in the lymph nodes in high numbers and travel around the blood strea,

Question 13

what activates a B lymphocyte

Answer 13

comes into contact with a pathogen, dendritic cell/acrophage or free virus particles that have the antigen complementary to the shape of the antigen binding site on its cell receptors

Question 14

once a b lymphocyte encounters dendritic cell/macrophage or free virus particles that have the antigen complementary to the shape of the antigen binding site on its cell receptors

Answer 14

Th b lymohcyte will engulf the pathogen by phagocytosis and present the antigens of the pathogen on its own MHC II markers, b lmphocyte is said to be selected

Question 15

once the b lymphocyte has been selected

Answer 15

the t helper cell with the complementary recpetor to the antigen will recognise the selected b cell and secrete cytokines which cause the b-lymphocyte to undergo clonaal expansion and differentiation, producing b memeory cells and plasma cells

Question 16

plasmaaa cells

Answer 16

differentiated clones of the the selected b lymphocyte, they secrete antibodies into the blood to defend against the specific pathogen, short lived cells

Question 17

b memeory cells

Answer 17

used for fast response to future exposure of the same pathogen, long lasting

Question 18

what are the five actions of antibodies

Answer 18

neutralisationn, aggultination, immobilisation, opsonisation and activation of complement proteins NAIOC

Question 19

neutralisation

Answer 19

block the sites of pathogens tthat are used to attack host cells

Question 20

agglutination

Answer 20

can bind with antigens on two seperate pathogens making it easier for phagocytes to recognise the pathogen as forgein and destroy it

Question 21

immobilisation

Answer 21

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

Question 22

opsonisation

Answer 22

bind directly to the surface of the pathogen to make it easier for phagocytosis to take place

Question 24

what is an antibody

Answer 24

a specific form of an immunoglobu;in, a protein found on the surface of a b cell, specific in nature

Question 25

structure of an antibody

Answer 25

2 heavy chains in the constant region, 2 light chains apart of both the constat and variable regions and two antiigen binding sites, composed of 4 polypeptide chains

Question 26

what are the five classes of antibody/immunoglobulin

Answer 26

IgA, IgD, IgE, IgG and IgM, each serve a different function

Question 27

epitope

Answer 27

a localised region on the surface of an antigen that is capable of eliciting an immune response and of combining with s dpecific antibdy to counter that response

Question 28

what occurs in the primary response

Answer 28

either by vaccination or natural exposure to an active pathogen/agent, their is a delay in the production of antibodies because of the need for clonal expansion and differentiation

Question 29

when does the secondary response occur

Answer 29

immunization booster, re-exposure to active pathogen/agent or a reaction to being exposed to the pathogen again

Question 30

how is the antibody production different in the secondary response on a graph

Answer 30

faster immune response and production of antibodies and more antibodies are produced, and they remain for a longer time

Question 31

why is the secondary response result in faster production of antibodies

Answer 31

there are many memory cells avaliable to the pathogen/agent, so there is no need for great clonal expansion, only a small amount of differentiation is required for memeory cells to be able to produce large amount of antibodies

Question 32

what is rhesus factor

Answer 32

a protein that is either present or absent on the surface of red blood cells

Question 33

if the rhesus factor is present

Answer 33

the blood is positive

Question 34

if the rhesus factor is absent

Answer 34

the blood is negative

Question 35

what is haemolytic disease

Answer 35

can occur in a newborn if there is rhesus incompatibility between the mother and her unborn child, occurs if the mother is negative and the father is positive and a positive baby is produced

Question 36

why is rhesus incompatibility harmful

Answer 36

if the positive blood from the baby enters the negative mothers blood stream, it will trigger an immune response as the rhesus protein will be recogniseed as an antigen

Question 37

how is haemuolytic disease treated

Answer 37

giving the mother a vaccination containing rhesus antiibodies, this blocks the antigens on the babies red blood cells that have entered the mothers blood stream, preventing an immune response and the build up of memory cells