Effect of Zbtb24-depletion on gene expressions during the activation of peritoneal B1 cells

ZBTB24-null ICF2 patients suffer from recurrent infections associated with antibody defects, implying a pivitol role of ZBTB24 in B cell biology. We thus generated B-cell specific Zbtb24 knockout mice and investigated its intrinsic role in B cell development and function both in vitro and in vivo. In accordance with findings obtained in ICF2 patients, Zbtb24 is dispensable for B cell developent and maintenance in mice. Strikingly, lack of Zbtb24 does not significantly compromise the primary & secondary antibody responses against TD-Ags, but reduced TID-Ags-elicited antibodies in vivo. At the cellular level, we discovered that Zbtb24-depletion specifically impaires the plasma cell (PC) differentiation of B1, but not the conventional B2 cells comprising follicular and marginal zone B cells, without impacting their survival and proliferation. Mechanistically, ablation of Zbtb24 suppresses the biosynthesis o heme in B1 cells, and supplementation of hemin largely abrogates the differentiation defects of zbtb24-null B1 cells in vitro. Our study not only provides a plausible explanation for the recurrent respiratory and gastrointestinal infections in ICF2 patients, but is also relevant for other B1 cell-mediated barrier defenses and immune regulations.