T follicular regulatory cells in mice and men

Summary It has long been known that CD 4 T cells are necessary to provide help to B cells, triggering a germinal centre ( GC ) reaction where affinity maturation and isotype switching occur. However, the nature of the dedicated CD 4 helper T cells, known as T follicular helper (Tfh), was only recently described. Here, we review the biology and function of the recently described T follicular regulatory (Tfr) cells, another CD 4 T‐cell population also found within GC s but with regulatory function and characteristics. Tfr cells have been identified in mice and humans as simultaneously presenting characteristics of T follicular cells (namely CXCR 5 expression) and regulatory T cells (including Foxp3 expression). These Tfr cells have been implicated in the regulation of the magnitude of the GC reaction, as well as in protection from immune‐mediated pathology.