PATHOLOGY

Detailed explanation-1: -B cells activate humoral immunity, whereas T cells activate cell-mediated immunity. The major difference between humoral and cell-mediated immunity is that humoral immunity produces antigen-specific antibodies, whereas cell-mediated immunity does not.

Detailed explanation-2: -Lymphocytes carry out both classes of responses. Here, the lymphocytes are responding to a viral infection. In one class of response, B cells secrete antibodies that neutralize the virus.

Detailed explanation-3: -Humoral immunity is also called antibody-mediated immunity. With assistance from helper T cells, B cells will differentiate into plasma B cells that can produce antibodies against a specific antigen.

Detailed explanation-4: -Helper T cells are arguably the most important cells in adaptive immunity, as they are required for almost all adaptive immune responses. They not only help activate B cells to secrete antibodies and macrophages to destroy ingested microbes, but they also help activate cytotoxic T cells to kill infected target cells.

Detailed explanation-5: -Th1 helper cells lead to an increased cell-mediated response (primarily by macrophages and cytotoxic T cells), typically against intracellular bacteria and protozoa. They are triggered by the polarising cytokine IL-12 and their effector cytokines are IFN- and IL-2.