Follicular helper T (Tfh) cells are a distinct subset of CD4+ helper T (Th) cells that regulate the development of antigen-specific B cell immunity. Upon exposure to a foreign antigen, Tfh cells help B cells generate antibody-producing plasma cells and long-lived memory B cells. Tfh cells are identified by elevated expression levels of multiple surface proteins and Bcl-6, as well as enhanced IL-21 secretion. The high expression levels of these proteins correlate with Tfh cells' enhanced capacity to facilitate antibody production. Tfh cells are believed to be involved in angioimmunoblastic T cell lymphoma and underlie several autoimmune diseases, including systemic lupus erythematosus and Sjogren's syndrome.
In the T cell zone of secondary lymphoid tissue, antigen-presenting dendritic cells activate naïve CD4+ T cells to produce IL-21. IL-6 and the autocrine action of IL-21 induce the activated CD4+ T cells to express Bcl-6, the master transcription factor that controls Tfh cell differentiation. Bcl-6, a transcriptional repressor, suppresses the expression of factors that mediate the differentiation of Th1, Th2 and Th17 cells, and clusters of miRNAs that negatively regulate molecules involved in Tfh functioning, such as the CXCR5. Increased expression of CXCR5 helps Tfh cells localize to B cell follicles, where they interact with germinal-centre B cells and secrete a variety of cytokines that stimulate B cells to generate antibody-producing plasma cells and memory B cells. R&D Systems offers a wide range of reagents to aid in Tfh cell research.