Overexpression of HIF-1α in RA synovial fibroblasts (RASFs) promoted expression of IL-6, IL-8, TNF-α, and IL-1β (82), and co-culturing HIF-1α-/- RASFs with allogenic CD19+ B cells down-regulated expression of stromal cell-derived factor (SDF)-1, vascular cell adhesion molecule (VCAM)-1, IgG and up-regulated percentage of CD19+CD24hiCD27+ B10 cells, CD19+CD27+IgD+ innate-like B cells, expression of natural IgM (82). Here, CD19 is linked to rheumatoid arthritis.