Catalytic diversity of polyclonal RNA-hydrolyzing IgG antibodies from the sera of patients with systemic lupus erythematosus.

Various catalytic antibodies or abzymes have been detected in the sera of patients with several autoimmune pathologies, and recently we have shown that RNase activity is associated with IgGs and IgMs from the sera of patients with systemic lupus erythematosus (SLE) but not with those from the sera of normal humans. Here we present for the first time convincing evidence showing that highly purified SLE IgG, its F(ab) fragments and separated L-chains catalyze RNA hydrolysis. These IgGs hydrolyze RNA about one to three orders of magnitude faster than DNA.

Catalytic heterogenity of polyclonal RNA-hydrolyzing IgM from sera of patients with lupus erythematosus.

Various catalytically active IgG antibodies or abzymes have been detected recently in the sera of patients with several autoimmune pathologies including systemic lupus erythematosus (SLE), where their presence is most probably associated with autoimmunization. Here we show for the first time that IgM from peripheral blood of patients with SLE possesses both DNase and RNase activities: these activities were also present in Fab fragments of the IgM. Both specific enzymic activities of IgM from sera of any single patient are usually 5-10 times higher than those of IgG antibodies.

RNA-hydrolyzing antibodies from peripheral blood of patients with lupus erythematosus.

Experiments and hydrolysis of substrates with known spatial structures (such as yeast tRNAPhe, as well as normal and mutant tRNALys from human mitochondria produced by transcription of the appropriate DNA species, that is, RNA genes) were performed to study the ribonuclease activity of antibodies isolated from blood sera of patients with systemic lupus erythematosus (SLE). The antibody preparations contained two types of ribonuclease activities: the first corresponded to the specificity of ribonuclease A and was found during hydrolysis at low salt concentrations, whereas the second was stimulated by Mg2+ and displayed unique specificity toward double-stranded regions of the substrate. The possible use of the antibody preparations as tools for structural studies of conformational differences between RNA molecules was examined.