PATHOLOGY

Detailed explanation-1: -In this chapter we will therefore use the term helper T cell to mean any armed effector CD4 T cell that can activate a B cell. Helper T cells also control isotype switching and have a role in initiating somatic hypermutation of antibody variable V-region genes, molecular processes that were described in Chapter 4.

Detailed explanation-2: -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-3: -B cell activation is initiated by the binding of antigen to the B cell receptor (BCR) that triggers a number of signaling cascades that ultimately lead to B cell activation.

Detailed explanation-4: -B cells activate humoral immunity, whereas T cells activate cell-mediated immunity.