Follicular B Helper T Cells

Follicular B helper T cells (also known as just Follicular helper T cells or T_FH), are antigen-experienced CD4+ T cells found in the B cell follicles of secondary lymphoid organs such as lymph nodes, spleens and Peyer's patches, and are identified by their constitutive expression of the B cell follicle homing receptor CXCR5. T_FH cells are found within B cell follicles and mediate antigen specific naïve or memory B cell activation, which triggers germinal center formation, probably through the expression of CD40L and the secretion of IL-21 and IL-4. It is possible that T_FH cells might arise as branches in the Th1 and Th2 differentiation pathways but their precise lineage relationship to the other effector CD4+ T cell subsets is still uncertain. Recent studies have however shown that T_FH have distinct gene expression profiles, supporting the theory that T_FH are a subset of CD4+ T cells distinct from Th-1, Th-2, Th-17 or Tregs.