Lec 33 - Ab distribution and function

Question 1

what type of immunity is achieved via vaccines?

Answer 1

induced active immunity

Question 2

what are the 2 types of vaccines? expand

Answer 2

component vaccines (RNA, DNA, virus-like particles, protein subunits, viral vectors)
whole vaccines (killed pathogen, live attenuated)

Question 3

what are the key functions of Abs? general

Answer 3

neutralisation (blocks pathogen-host binding, cant exert their effect)

opsonisation (enhance phagocytosis of macrophages, etc)

complement fixation (C1q binding, classical activation)

Ab-dependent mediated cytotoxicity (NK induced)

trigger degranulation via Fc

transport (for all of the above)

Question 4

what do Fc recepotrs bind to?

Answer 4

Fc portion of Abs
each type of Fc receptor can only bind to one class of Ig (binding is class specific, not one fits all)

Question 5

where are Fc receptors found?

Answer 5

on a lot of innate immune cells

Question 6

what is the role of Fc receptors?

Answer 6

mediate many effector Ab functions only if Fc receptor is crosslinked to Fc and Ab is actually bound to Ag (leads to conformational change in Fc)

Question 7

what are effector functions that result from Fc-Fcr binding?

Answer 7

degranulation and histamine release by Mast cells

Question 8

how are innate immune cells able to be somewhat specific?

Answer 8

via specific Fc receptors

Question 9

what does opsonisation require?

Answer 9

Fc receptors on macrophage binding to Fc of Ab on pathogen

aggregation of binding will lead to cross-linking, triggering intracellular signaling leading to effector functions

Question 10

what are IgG effector functions?

Answer 10

enhance phagocytosis by macrophages (opsonisation)

other functions depends on IgG subclass

some effective at complement fixation, other mediating ADCC by NK cells (function = toxic granule release)

Question 11

what are effector functions of IgE?

Answer 11

degranulation of eosinophils/basophils
histamine release by mast cells

Question 12

can IgE bind to mast cell before Ag is bound to Ab?

Answer 12

yes, wont perform effector function though
requires Fc-Fcr crosslinking to lead to histamine release

is not just specific to IgE, is the case for all Ig classes and effector functions

Question 13

what pathogens can be neutralised?

Answer 13

any intracellular pathogen
toxin, virus, bacteria

Question 14

what Ig isotypes are good for neutralisation?

Answer 14

IgA and IgGw

Question 15

where is IgA found majority of the time?

Answer 15

secretions: gut mucus, mammary gland milk, tears, saliva

Question 16

how does C1q bind to pathogen?

Answer 16

directly or via Abs on surface

Question 17

which Ig isotypes can trigger complement cascade? expand

Answer 17

IgM and IgG

especially IgM because of pentavalent, creating nice landing pad for C1q

Question 18

what else is IgM good for?

Answer 18

forming dense Ab-pathogen complex (since 10 binding sites), allowing efficient engulfing by macrophage

Question 19

how does transport differ between Ig classes? expand

Answer 19

go to different parts of the body
IgA = found in mucosal tissues
IgE = near epithelial surfaces
IgM = blood (but not high quantity)
IgG = widely distributed (inc. fetus)

Question 20

A
B5
C
D
E4