Aryl hydrocarbon receptor modulates the development and activity of innate-like B cells (HEM1P.226)

The Aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor that recognizes polyaromatic hydrocarbons. While the contributions of AhR ligands to the differentiation and functions of Th17/Treg cells are relatively well understood, little is known about AhR in B cells. Microarray and quantitative PCR analysis of B cell subsets revealed that B1 and marginal zone (MZ) B cells expressed higher levels of AhR compared to follicular (FO) B cells. We found ~ two-fold more B1 B cells, but fewer MZ B cells in AhR-/- mice compared to AhR+/+ mice. Following immunization with Streptococcus pneumonia, AhR-/- mice had significantly higher titers of anti-phosphorylcholine IgM antibodies. In contrast, after immunization with a model T cell-dependent antigen, Trinitrophenyl Keyhole Limpet Hemocyanin (TNP-KLH), AhR-/- mice had anti-TNP titers that were comparable to those in AhR+/+ mice. Further, we found significantly fewer B cells in C57BL/6 mice raised on AhR ligand free diet, and an increase in titers of IgM and IgG3 in mice following a switch to an AhR ligand free diet when compared to littermates raised and maintained on conventional diet. Taken together, these findings suggests that AhR plays a role in the development of B1 and MZ B cells and regulates T cell-independent but not T cell-dependent humoral response. Further studies using mice with a B cell specific deletion of AhR are underway to elucidate the mechanism by which AhR ligands influence humoral immunity.