Antibodies to nucleic acids in systemic lupus erythematosus and rheumatoid arthritis patients and their relatives.

Sera of systemic lupus erythematosus (SLE) patients contain antibodies to double-stranded and single-stranded DNA while antibodies found in rheumatoid arthritis sera are specific mainly to single-stranded DNA. Anti-RNA antibodies in the both cases are directed against double-stranded RNA and belong to the IgM class while anti-DNA antibodies are IgG. Genetic variance analysis based on family correlations suggests that the synthesis of antibodies to DNA is subject to different modes of gene regulations in systemic lupus erythematosus and rheumatoid arthritis patients. In the case of SLE, a high degree of genetic determination is demonstrated, due mainly to the X-chromosomal component of the general phenotypic variance. The failures in the immunoregulation system that are responsible for anti-RNA antibody production are rather similar in the two groups of patients and involve a combination of environmental and autosomal factors.