adaptive immunity (effector mechanisms) (W11)

Question 1

antibody different name and 5 types?

Answer 1

immunoglobulin (Ig)
IgM, IgG, IgA, IgE, IgD

Question 2

antibody neutralisation?

Answer 2

neutralises virulence factors - bind to components to stop them binding to the receptors on our cells

Question 3

IgM structure?

Answer 3

5 antibodies linked together

Question 4

which antibodies can activate the classical complement pathway

Answer 4

IgM and IgG

Question 5

how do antibodies opsonise cells and drive phagocytosis

Answer 5

phagocytes have receptors on their surface for antibodies (Fc receptors). pathogens with antibodies on their surface have been opsonised, antibodies engage Fc receptors and drive phagocytosis

Question 6

ADCC?

Answer 6

antibody-dependant cell cytotoxicity:
antibodies bind to pathogen molecules on infected cells surfaces
NK cells and neutrophils recognise antibodies and cause apoptosis vis cytotoxic granules

Question 7

what receptors do mast cells and basophils have which bind to what

Answer 7

Fc receptors that bind to free IgE

Question 8

what are mast cells and basophils particularly active in

Answer 8

anti-worm/allergy responses

Question 9

what happens when IgE binds to mast cells

Answer 9

cross linking of IgE receptors triggering the mast cells to granulate releasing histamine

Question 10

what happens when there is systemic mast cell degranulation

Answer 10

anaphylactic shock

Question 11

what determines antibody function

Answer 11

Fc region (constant region) - isotypes

Question 12

antibodies expressed by naïve B cells

Answer 12

IgM and IgD (not secreted, just on surface as a receptor)

Question 13

what is class switching?

Answer 13

activated B cells can class switch to make IgG, IgA, IgE

Question 14

different Fc receptors for each antibody isotype?

Answer 14

Fc-gamma for IgG
Fc-epsilon for IgE
Fc-alpha for IgA
Fc-mu for IgM

Question 15

function of IgM

Answer 15

good at trapping and neutralising antigen
not good at opsonising and ADCC

Question 16

function of IgA

Answer 16

good at neutralizing intestinal pathogens and ensuring they are flushed out
poor at activating complement, opsonising and ADCC

Question 17

function of IgG

Answer 17

action depends on subclass - can opsonise, neutralise, activate complement and ADCC depening

Question 18

function of IgE

Answer 18

best for activating basophils, mast cells and eosinophils (in allergy and infection)

Question 19

B cell activation and somatic hypermutation?

Answer 19

after B cell activation, point mutations in variable regions of receptor/antibody resulting in antigens with stronger/weaker binding to antigen. Stronger ones selected by affinity maturation.

Question 20

why is affinity maturation in IgG important

Answer 20

IgG is monomeric - only one attachment site so must be strong

Question 21

Th1 cytokine produced and function?

Answer 21

IFN-gamma
vs intracellular bacteria + viruses

Question 22

Th2 cytokine produced and function?

Answer 22

IL-4
vs parasitic worms

Question 23

Th17 cytokine produced and function?

Answer 23

IL-17
vs extracellular bacteria and fungi

Question 24

Treg cytokine produced and function?

Answer 24

IL-10
suppresses immune responses

Question 25

CD4+ helper cells functions?

Answer 25

provide co-stimulation to B cells
drive affinity maturation of B cells
drive class-switching of B cells
Activate innate immune cells

Question 26

how do CD4+ T cells help B cells

Answer 26

providing signal 2 (only when B cells present them with peptide/MCH2 that they recognise)

Question 27

what does linked recognition (following somatic hypermutation) by CD4+ T cells allow

Answer 27

selection of B cells expressing receptors/antibodies that bind antigen most strongly, therefore driving affinity maturation

Question 28

what does class-switching require from CD4+ T cells

Answer 28

co-stimulation

Question 29

CD4+ T cells stimulate innate cells (help brain doesn’t work)

Answer 29

AHHHHH

Question 30

2 mechanisms that CD8+ CTL use to kill

Answer 30

FAS ligation
perforin and granzyme release

Question 31

FAS ligation?

Answer 31

directly signals to induce apoptosis

Question 32

perforin and granzyme release?

Answer 32

perforin makes pore in cell allowing granzyme to enter. this activates caspases, DNAase activation and mitochondrial breakdown.