Studies of a common idiotype PR4 in autoimmune rheumatic disease.

A new common idiotype, designated PR4, is described. This idiotype was originally identified on a human hybridoma-derived monoclonal antibody from a patient with leprosy, which binds the major Mycobacterium leprae-derived antigen, phenolic glycolipid-1, poly(ADP)-ribose, DNA, and poly(dT). The PR4 idiotype was found in patients with systemic lupus erythematosus (SLE) (70%), rheumatoid arthritis (40%), and Sjögren's syndrome (15%). It was not, however, found in the spouses of the SLE patients or (unlike other lupus idiotypes) in their healthy first-degree relatives. Although no correlation between PR4 idiotype levels and disease activity in SLE was found, a subset of rheumatoid arthritis patients with high levels of the idiotype was identified.