effector B cells

Question 1

AID

Answer 1

AID enzyme looks for cytidine rings and changes the NH2 group into a double stranded O (C nucleotide to U nucleotide)

targets switch a switch region and induces nicks either side of the other genes upstream of the switch region, causing double stranded breaks. Eventually, the DNA repair machinery will repair these breaks by excising the loop of DNA between the nicks

Question 2

How is class switching mediated

Answer 2

Class switching is mediated by cytokines. In particular, polarising cytokines IL-4 and IFN-gamma promote class switching to IgE or IgG, respectively

Question 3

IgA

Answer 3

dimeric, needs to be transported across membranes, is in mucosal secretions
can activate complement

Question 4

IgG

Answer 4

general purpose antibody, small enough to cross tissue barriers without transport, better at its job than IgM, can activate complement, crosses placenta

Question 5

IgM

Answer 5

pentameric, so has poor tissue penetration, general purpose, can activate complement, better at recognising repeative antigens

Question 6

IgE

Answer 6

targets large parasites, good activator of mast cells, cannot activate complement

Question 7

ADCC

Answer 7

Ig binds to natural killer cell via FcgammaRIII receptor, cross linking of FcR triggers NK cell killing

Question 8

degranulation

Answer 8

IgE binds to FcepsilonRI on immune cell, cross linking triggers degranulation

Question 9

what antibodies neutralise

Answer 9

IgG, IgM, IgA