Question

It is said, "No T cells, no immunity." How can this statement be explained?

Answer 1

T cells are the first line of defence in the immune system, without which the rest of the immune system cannot get activated.

Explanation:

T cells or T lymphocytes (T because they originate in the thymus) are the first line of defense of the body's immune system.

They are the ones to recognise a pathogenic or a foreign antigen, and activate the rest of the immune system to neutralise it. Some T cells can even create memory cells that enable the host to have lifelong immunity to certain pathogens.