In addition, adaptive immune cell infiltration in ACPA-negative RA synovium was lower than that in ACPA-positive RA synovium but still significantly higher than that in OA and HCs control, which implied that most of patients with ACPA-negative RA may have unknown autoantibodies that were still undiscovered or have delayed appearance of the conventional autoantibodies. The gene discussed is PRTN3; the disease is rheumatoid arthritis.