Effector Responses of IS

Question 1

Effector responses

Answer 1

aim to eliminate pathogens and infected cells from the body + clear cells that are damaged or abnormal

Question 2

Name the antibody isotopes.

Answer 2

IgM - produced 1st during infection
IgG - abundant in blood
IgA - in mucous membranes
IgE - against worm infection

Question 3

What are the differences between the antibody isotopes?

Answer 3

~ differ in their Fc regions and hinge

~ diff. effector functions, depend on which Fc receptors they bind to

Question 4

Name the functions of antibodies.

Answer 4

1) neutralisation
2) opsonisation
3) complement fixation
4) antibody-dependent cell-mediated cytotoxicity (ADCC)
5) Activation of granulocytes

Question 5

Neutralisation

Answer 5

~ antibody binding to the surface of a virus can prevent cell entry
~ antibodies can bind toxins from bacteria, making them harmless

Question 6

Opsonisation

Answer 6

~ IgG and IgA surround pathogens can bind to Fc receptors (FcR) on macrophages
~ induces phagocytosis and the digestion of pathogens in lysosomes
~ can work together to make this happen

Question 7

Complement fixation

Answer 7

~ IgG and IgM are recognised by the C1 complement complex –> activation of the classical complement pathway
~ this induces 1) optimisation by C3b and phagocytosis 2) lysis of the pathogen or the infected cell using the membrane attack complex (MAC)

Question 8

Antibody-dependent cell-mediated cytotoxicity (ADCC)

Answer 8

~ IgG on the surface of infected cells binds to the FcgRIIIa receptor on Natural killer cells
~ this induces the degranulation of NK cells
~ NK cells granules contain performs and granzymes which induce apoptosis

Question 9

Activation of granulocytes

Answer 9

~ IgE bound to parasites or allergens causes the degranulation of mast cells, eosinophils and basophils
~ this induces the release of histamine and other inflammatory mediators
~ this activates T(H)2 cells during

Question 10

Name the cytotoxic effector cells

Answer 10

~ NK cells
~ CD8+ cytotoxic T lymphocytes (CTLs)
~ NK T-cells
~ all induce death by apoptosis
~ climate cells infected with intracellular pathogens, tumour or damaged cells

Question 11

Generation of cytotoxic T-cells.

Answer 11

1) licensing of an antigen presenting cell (APC) - interaction w/ pathogen or activated T(H)1 cell
2) interaction of licensed APC w/ naïve CD8+ T-cell –> activation + differentiation into cytotoxic T-cell (CTL)
3) simultaneous interaction of APC with activated T(H)1 cell + CD8+ T-cell –> APC licensing + CD8+ T-cell activation
~ IL-2 (from T(H)1) promotes CTL differentiation = efficient

Question 12

Action of cytotoxic T lymphocytes a.k.a. ‘kiss of death’

Answer 12

1) CTL forms immunological synapse w/ target cell
2) secretory granules move along microtubules
3) secretory granule fuse with the presynaptic men.
4) perforins assemble to make pores, granzyme causes apoptosis of target cell

Question 13

Perforins

Answer 13

~ monomers that assemble in the membrane of target cell to form a pore

Question 14

Granzymes

Answer 14

~ serine proteases that cleave proteins in the target cell

~ enter through the pore created by perforins

Question 15

Natural killer T-cells (5).

Answer 15

a.k.a. NKT cells
~ type of T lymphocyte w/ similar properties to NK cells
~ develop in thymus
~ undergo TCR gene rearrangements BUT express invariant TCR = alpha-beta TCR –> recognises CD1d (non-classical MHC)
~ act as both helper + cytotoxic cells (inc. CD4- + CD4+)
~ lack some T-cell markers but have other