Serological abnormalities, including common idiotype PR4, in families with rheumatoid arthritis.

A broad range of autoreactivity among a group of 12 French patients with rheumatoid arthritis (RA) and 58 of their healthy first degree relatives has been identified. Over 15% of the patients were found to have antibodies to ssDNA, histone H1, H2A, and H2bB. Among the relatives, IgG and IgM rheumatoid factor and antibodies to ssDNA, H2A, and H4 were present in more than 10%. Even more remarkable, a common anti-DNA antibody idiotype designated PR4, known to be present in 70% of patients with systemic lupus erythematosus (SLE), was found in approximately 30% of both patients with RA and their healthy relatives. This is quite different from its lack of increased expression in relatives of patients with SLE and suggests that in the family members of those with RA a particular combination of environmental influence on germline gene expression is responsible.