Interferons are:

Which of the following is responsible for the rejection of organ transplants?

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

Match the type of immunity listed in Column-$I$ with the examples listed in Column-$II$. Choose the answer that gives the correct combination of alphabets of the two columns:

Column-$I$ (Types of immunity)	Column-$II$ (Example)
$A$. Natural active	$p$. Immunity developed by heredity
$B$. Artificial passive	$q$. From mother to foetus through placenta
$C$. Artificial active	$r$. Injection of antiserum to travellers
$D$. Natural passive	$s$. Fighting infections naturally
	$t$. Induced by vaccination

Bone marrow is included in:

What type of barrier is the mucus membrane?