Introduction of attenuated pathogens in human body results in . . . . . . .

Except for the skin,other physical barriers that also help to prevent the entry of microorganisms are:
$I.$ Mucus coating of the epithelium lining the respiratory tract
$II.$ Gastrointestinal tract
$III.$ Urogenital tract
Choose the correct option.

Acquired immunity is mediated by which of the following?

Who is known as the father of immunology?

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.

Where are $B$-cells and $T$-cells formed? How do they differ from each other?