Functional differentiation and regulation of follicular T helper cells in inflammation and autoimmunity.

Follicular T helper (T ) cells are specialized T cells that support B cells, which are essential for humoral immunity. T cells express the transcription factor B-cell lymphoma 6 (Bcl-6), chemokine (C-X-C motif) receptor (CXCR) 5, the surface receptors programmed cell death protein 1 (PD-1) and inducible T-cell costimulator (ICOS), the cytokine IL-21 and other molecules. The activation, proliferation and differentiation of T cells are closely related to dynamic changes in cellular metabolism. In this review, we summarize the progress made in understanding the development and functional differentiation of T cells. Specifically, we focus on the regulatory mechanisms of T cell functional differentiation, including regulatory signalling pathways and the metabolic regulatory mechanisms of T cells. In addition, T cells are closely related to immune-associated diseases, including infections, autoimmune diseases and cancers.