CD79A and rheumatoid arthritis: Unlike the isotypes of RF, where various isotypes (IgM > IgA > IgG) were found [31], the enrichment of IgG and IgA isotypes and an early increase in IgG, particularly IgG1 subclasses, frequency and concentration, were found to dominate in the serum of patients with RA, or to precede the development of the disease [31,34,35,36].