IL6 and rheumatoid arthritis: IL-6 is produced by fibroblasts, MNs, and T and B cells.62,71 In RA patients, the concentration of IL-6 in the blood and synovium is increased compared to that in healthy donors and is associated with joint damage.71 In RA treatment, the IL-6 receptor inhibitors tocilizumab and sarilumab are used as monotherapy or in combination with methotrexate.71