Acquired immunity is due to

The antibodies are:

Which of the following are included in primary lymphoid organs?

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.

Which of the following cells has the longest lifespan?

In our society,....... is an auto-immune disease.