Against which of the following does interferon act

Given below the diagrammatic representation of lymph nodes

Label $A, B$ and $C$

$MALT$ constitutes about _______ percent of the lymphoid tissue in human body.

Grafted kidney may be rejected in a patient due to

$A$ : Colostrum is a very efficient means of transferring immunity to a newborn.
$R$ : IgM from mother’s milk protects the baby from the respiratory infection usually affecting in young age.