B-cell interleukin 1 receptor 1 modulates the female adipose tissue immune microenvironment during aging.

Myeloid cell production of interleukin-1β (IL-1β) drives inflammaging in visceral white adipose tissue (vWAT) and contributes to the expansion of interleukin-1 receptor 1 (Il1r1)-positive aged adipose B cells (AABs). AABs promote metabolic dysfunction and inflammation under inflammatory challenges. However, whether IL-1β contributes to AAB-associated inflammation during aging is unclear. Using a B-cell-specific knockout of Il1r1 (BKO mice), we characterized old vWAT in the absence of IL-1β-B-cell signaling. In addition to sex-specific metabolic improvements in females, we identified a reduction in the proportion of B cells and a sex-specific increase in the B1/B2 B-cell ratio in BKO vWAT. Using single-cell RNA sequencing of vWAT immune cells, we observed that BKO differentially affected inflammatory signaling in vWAT immune cells. These data suggest that IL-1β-B-cell signaling supports the inflammatory response in multiple cell types and provides insight into the complex microenvironment in aged vWAT.