How follicular T-helper （Tfh） cells develop is incom- pletely understood. We find that, upon antigen exposure in vivo, both naive and antigen-experienced T cells sequentially upregulate CXCR5 and Bc16 within the fir...How follicular T-helper （Tfh） cells develop is incom- pletely understood. We find that, upon antigen exposure in vivo, both naive and antigen-experienced T cells sequentially upregulate CXCR5 and Bc16 within the first 24 h, relocate to the T-B border, and give rise to phenotypic Bcl6＋CXCR5＋ Tfh cells before the first cell division. CXCR5 upregulation is more dependent on ICOS costimulation than that of Bcl6, and early Bcl6 induction requires T-cell expression of CXCR5 and, presumably, relocation toward the follicle. This early and rapid upregulation of CXCR5 and Bcl6 depends on IL-6 produced by radiation-resistant cells. These results suggest that a Bcl6hiCXCR5hi phenotype does not automatically define a Tfh lineage but might reflect a state of antigen exposure and non-commitment to terminal effector fates and that niches in the T-B border and/or the follicle are important for optimal Bcl6 induction and maintenance.展开更多
文摘How follicular T-helper （Tfh） cells develop is incom- pletely understood. We find that, upon antigen exposure in vivo, both naive and antigen-experienced T cells sequentially upregulate CXCR5 and Bc16 within the first 24 h, relocate to the T-B border, and give rise to phenotypic Bcl6＋CXCR5＋ Tfh cells before the first cell division. CXCR5 upregulation is more dependent on ICOS costimulation than that of Bcl6, and early Bcl6 induction requires T-cell expression of CXCR5 and, presumably, relocation toward the follicle. This early and rapid upregulation of CXCR5 and Bcl6 depends on IL-6 produced by radiation-resistant cells. These results suggest that a Bcl6hiCXCR5hi phenotype does not automatically define a Tfh lineage but might reflect a state of antigen exposure and non-commitment to terminal effector fates and that niches in the T-B border and/or the follicle are important for optimal Bcl6 induction and maintenance.
