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.