Cutting Edge: Retinoic Acid Signaling in B Cells Is Essential for Oral Immunization and Microflora Composition.

Retinoic acid (RA) is a critical regulator of the intestinal adaptive immune response. However, the intrinsic impact of RA on B cell differentiation in the regulation of gut humoral immunity in vivo has never been directly shown. To address this issue, we have been able to generate a mouse model where B cells specifically express a dominant-negative receptor α for RA. In this study, we show that the silencing of RA signaling in B cells reduces the numbers of IgA(+) Ab-secreting cells both in vitro and in vivo, suggesting that RA has a direct effect on IgA plasma cell differentiation. Moreover, the lack of RA signaling in B cells abrogates Ag-specific IgA responses after oral immunization and affects the microbiota composition. In conclusion, these results suggest that RA signaling in B cells through the RA receptor α is important to generate an effective gut humoral response and to maintain a normal microbiota composition.