Obesity induces pro-inflammatory B cells and impairs B cell function in old mice.

We analyzed B cells infiltrating the Visceral Adipose Tissue (VAT) of young and old mice to identify contributors to the phenotypic and functional changes observed in aged B cells. We found higher percentages of pro-inflammatory (age-associated B cells, ABC) and less Follicular (FO) B cells in VAT as compared to spleen. VAT B cells express higher pro-adipogenic and inflammatory markers, including NF-kB, as compared to splenic B cells, and also secrete IgG2c antibodies, some of which have been shown to be autoimmune in other studies. Moreover, we found that in the presence of an adipocyte-conditioned medium FO B cells differentiated into ABC. Additional results showed production of pro-inflammatory chemokines by the adipocytes, suggesting a mechanism for B cell attraction by the VAT. These results are the first to show a direct effect of adipocytes on the generation of pro-inflammatory B cells.