Differential regulation of IgA+ B cells in vitro by stromal cells from distinctive anatomical compartments

B cell development is regulated by stromal cells (SCs) that form a supportive microenvironment. These SCs along with other cell types produce cytokines, chemokines, and adhesion molecules that guide B cell commitment and differentiation. BM, spleen (Sp), and the gut lamina propria (LP) constitute distinctive anatomical compartments that support B cell differentiation. In order to characterize and compare the signals necessary to generate IgA+ B cells, we developed an in vitro system to co‐culture gut LP, BM, or Sp‐derived SCs with B lineage cells. Using this co‐culture system, we found that gut LP SCs promote IgA+ B cell accumulation through the production of soluble stimulatory factors. In contrast to gut LP SCs, BM and splenic SCs were found to impair IgA+ B cell accumulation in vitro. Taken together, these observations provide new insights into how SCs derived from different anatomical locations shape IgA+ B cell responses. Accumulation of IgA+ B cells in vitro is enhanced by gut lamina propria stromal cells but inhibited by bone marrow and splenic stromal cells.