ThF

Follicular helper T cells, or ThF cells, are antigen-experienced CD4⁺ T cells found in the lymph node and are identified as being PSGL-1- and CXCR5+. [cite journal |author=Campbell DJ, Kim CH, Butcher EC |title=Separable effector T cell populations specialized for B cell help or tissue inflammation |journal=Nature immunology |volume=2 |issue=9 |pages=876–81 |year=2001 |month=September |pmid=11526405 |doi=10.1038/ni0901-876 |url=http://dx.doi.org/10.1038/ni0901-876] cite journal |author=Akiba H, Takeda K, Kojima Y, "et al" |title=The role of ICOS in the CXCR5+ follicular B helper T cell maintenance in vivo |journal=Journal of immunology (Baltimore, Md. : 1950) |volume=175 |issue=4 |pages=2340–8 |year=2005 |month=August |pmid=16081804 |doi= |url=http://www.jimmunol.org/cgi/pmidlookup?view=long&pmid=16081804] ThF cells are found at the periphery of B cell follicles and appear to mediate naïve B cell activation and germinal center formation, probably through the expression of ligand for CD40 and the secretion of Th1– and Th2-like cytokines. It is possible that ThF 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.

Inducible T-cell co-stimulator ("CD278" or "ICOS") has proven to be a particularly critical signal for ThF cells, although it is not clear if that role is in induction or progressive maturation.cite journal |author=Vinuesa CG, Cook MC, Angelucci C, "et al" |title=A RING-type ubiquitin ligase family member required to repress follicular helper T cells and autoimmunity |journal=Nature |volume=435 |issue=7041 |pages=452–8 |year=2005 |month=May |pmid=15917799 |doi=10.1038/nature03555 |url=http://dx.doi.org/10.1038/nature03555] Also Bcl-6 is a factor identified in ThF cells, but it may have roles that extend beyond this subset, because it has been implicated in memory CD8⁺ T cell development. [cite journal |author=Chtanova T, Tangye SG, Newton R, "et al" |title=T follicular helper cells express a distinctive transcriptional profile, reflecting their role as non-Th1/Th2 effector cells that provide help for B cells |journal=Journal of immunology (Baltimore, Md. : 1950) |volume=173 |issue=1 |pages=68–78 |year=2004 |month=July |pmid=15210760 |doi= |url=http://www.jimmunol.org/cgi/pmidlookup?view=long&pmid=15210760] [cite journal |author=Ichii H, Sakamoto A, Hatano M, "et al" |title=Role for Bcl-6 in the generation and maintenance of memory CD8+ T cells |journal=Nature immunology |volume=3 |issue=6 |pages=558–63 |year=2002 |month=June |pmid=12021781 |doi=10.1038/ni802 |url=http://dx.doi.org/10.1038/ni802]

Finally, it has been shown that dysregulated ThF cells can cause systemic autoimmunity and auto-antibody production or contribute to T cell–mediated organ-specific autoimmunity.

References