C17orf99 and rheumatoid arthritis: Also, serum IL-40 is increased in RA patients compared to OA, HC or SLE [5.4 (12.0-22.2) vs. 1.4 (0.6-3.1), 1.4 (1.0-1.9) or 1.5 (0.7-2.7) ng/ml, respectively; p<0.0001 for all], (Figure 3B).