Antibodies are produced by

In which of the following organs do immature lymphocytes differentiate into antigen-sensitive lymphocytes?

Fill in the blanks: Our body, when it encounters a pathogen for the first time, produces a response called . . . . . . $a$ . . . . . . response, which is of . . . . . . $b$ . . . . . . intensity. Subsequent encounters with the same pathogen elicit a . . . . . . $c$ . . . . . . intensified . . . . . . $d$ . . . . . . response.

$T$-lymphocytes differentiate in which of the following organs?

Which immunoglobulin is present in abundant amounts in the mother's initial milk secretion (colostrum)?

$MALT$ constitutes about ................. of the lymphoid tissue in the human body. (in $\%$)