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Memory B cells contribute to rapid Bcl6 expression by memory follicular helper T cells (Tomohiro KUROSAKI in PNAS)
In primary humoral responses, Bcl6 is a master regulator of TFH differentiation; however its activation mechanisms and role in memory responses remain unclear.
The authors demonstrate that survival of CXCR5+ TFH memory cells and thus subsequent recall antibody response require Bcl6 expression. Furthermore, they show that, upon re-challenge with soluble antigen, Bcl6 in memory TFH cells is rapidly induced in a dendritic cell-independent manner, and that peptide:class II complexes (pMHC) on cognate memory B cells significantly contribute to this induction. Given the previous evidence that antigen-specific B cells residing in the follicles acquire antigens within minutes of injection, their results suggest that memory B cells present antigens to the cognate TFH memory cells, thereby contributing to rapid Bcl6 re-expression and differentiation of the TFH memory cells during humoral memory responses.
Immunology Frontier Research Center (WPI-IFReC), Osaka University