TNFSF13B and rheumatoid arthritis: TNFSF13B, which encodes the B-cell activating factor (BAFF), was upregulated in ITGB2(+) macrophages in both RA and MN, enhancing interactions between macrophages and B cells (TNFSF13B-TNFRSF13C) or plasma cells (TNFSF13B-TNFRSF17) (Figure 7E,J).