Innate response activator B cells are sentinels that guard against polymicrobial sepsis. Mus musculus

Innate immunity is fundamental to recognition and clearance of bacterial infection. The relevant cells and molecules that orchestrate an effective response, however, remain incompletely understood. Here we describe a previously unknown population of B cells, which we have named innate response activator (IRA) B cells that recognize bacteria directly through TLR-4-MyD88 and protect against polymicrobial sepsis. IRA-B cells have a unique IgM high CD23 low CD43 + CD93+ GM-CSF+ signature, develop and diverge from B1a B cells, require BAFFR, and adhere to tissue via VLA-4 and LFA-1. Overall design: B cell subsets are sorted from the spleen and peritoneum of C57BL/6 mice that were given intraperitoneal injections of LPS once daily for four days.