Anti-poly(G) . poly(C) antibodies in the serum of patients with systemic lupus erythematosus.

Antibodies reacting with the double-stranded synthetic polyribonucleotide complex poly(G)·poly(C) have been demonstrated with various titers in the sera of patients with systemic lupus erythematosus (SLE). Despite a few exceptions, high poly(G)·poly(C) binding activity appears to be associated with clinically active disease. In contrast, there was no anti-poly(G)·poly(C) activity in the sera of normal subjects, or of patients with scleroderma, rheumatoid arthritis, and most of the sera from patients with mixed connective tissue disease. The poly(G)·poly(C) reactive antibodies were found to belong to the IgG class. They appeared to be different from those directed against poly(A)·poly(U) and poly(I)·poly(C). Competition experiments showed that in the majority of cases the most efficient inhibitor after poly(G)·poly(C) was total RNA from mammalian cells. Besides this cross-reactivity, the most striking feature of anti-poly(G)·poly(C) antibodies was their wide heterogeneity, each serum possessing its own specificity.