IL37 and rheumatoid arthritis: Furthermore, IL-35 and IL-37 are anti-inflammatory cytokines belonging to the IL-12 and IL-1 families.19 Their recruitment reduces inflammation in several autoimmune disorders, including multiple sclerosis, psoriasis, and rheumatoid arthritis.19 IL-35/IL-37 is primarily produced by regulatory T cells (Tregs) and regulatory B cells.