FLS in RA prolong the lifespan of B cells by generating IL-6, vascular cell adhesion molecule 1 (VCAM1), CXC chemokine ligand 12 (CXCL12), B cell-activating factor (BAFF; also known as TNFSF13B), and a proliferation-inducing ligand (APRIL; also known as TNFSF13) 82. This evidence concerns the gene TNFSF13 and rheumatoid arthritis.