Studies have shown the presence of specific anti-chondrocyte membrane antibodies (ACMA) in the sera of RA and OA patients, which are highly specific and bind only to chondrocyte surface proteins (CH65, CD38, CD30, CD28) and not to collagen cell membranes, fibroblast membranes, and pancreatic tumor cell membranes. This evidence concerns the gene CD38 and rheumatoid arthritis.