T Follicular Helper Cells

Protective humoral responses, elicited by infection or vaccination, require the provision of help to B cells by specialized T follicular helper (Tfh) cells. These T-B interactions are critical for the isotype switching and affinity maturation of B cells leading to the production of high-affinity antibodies. Tfh cells differentiate from naïve CD4 + T cells through a two-step process, first determined by activation by antigen-presenting cells, followed by cognate interactions with B cells. Outside the follicle and within the germinal center (GC), Tfh cells provide crucial signals to B cells through CD40L and the production of IL-21 and IL-4, to support GC development and function.