$MALT$ constitutes about what percentage of the lymphoid tissue in the human body (in $, \%$)?

Which memory cells are produced during vaccination?

What is a vaccine?

Which substance protects non-infected cells from viral infection?

$A$ substance (low molecular weight protein) produced by host cells in response to viral infection that protects other cells against further viral infection is:

Which of the following acts as a physical barrier to prevent the entry of microorganisms into our body?