CA3 and rheumatoid arthritis: In the present study, we determined the antibodies response to the CA III and CA IV in the serum of Chinese patients with RA, systemic lupus erythematosus (SLE), type 1 diabetes (T1D), type 1 diabetic nephropathy (T1DN), type 2 diabetes (T2D), type 2 diabetic nephropathy (T2DN), hypertensive nephropathy, and heart failure using indirect enzyme-linked immunosorbent assay (ELISA) and investigated the possible associations between these antibodies and other indicators of these diseases.