AUTHOR=Fu Ying , Wang Zhiming , Yu Baichao , Lin Yuli , Huang Enyu , Liu Ronghua , Zhao Chujun , Lu Mingfang , Xu Wei , Liu Hongchun , Liu Yongzhong , Wang Luman , Chu Yiwei TITLE=Intestinal CD11b+ B Cells Ameliorate Colitis by Secreting Immunoglobulin A JOURNAL=Frontiers in Immunology VOLUME=12 YEAR=2021 URL=https://www.frontiersin.org/journals/immunology/articles/10.3389/fimmu.2021.697725 DOI=10.3389/fimmu.2021.697725 ISSN=1664-3224 ABSTRACT=

The intestinal mucosal immune environment requires multiple immune cells to maintain homeostasis. Although intestinal B cells are among the most important immune cells, little is known about the mechanism that they employ to regulate immune homeostasis. In this study, we found that CD11b+ B cells significantly accumulated in the gut lamina propria and Peyer’s patches in dextran sulfate sodium-induced colitis mouse models and patients with ulcerative colitis. Adoptive transfer of CD11b+ B cells, but not CD11b−/− B cells, effectively ameliorated colitis and exhibited therapeutic effects. Furthermore, CD11b+ B cells were found to produce higher levels of IgA than CD11b− B cells. CD11b deficiency in B cells dampened IgA production, resulting in the loss of their ability to ameliorate colitis. Mechanistically, CD11b+ B cells expressed abundant TGF-β and TGF-β receptor II, as well as highly activate phosphorylated Smad2/3 signaling pathway, consequently promoting the class switch to IgA. Collectively, our findings demonstrate that CD11b+ B cells are essential intestinal suppressive immune cells and the primary source of intestinal IgA, which plays an indispensable role in maintaining intestinal homeostasis.