Defective degradation of bacterial DNA by phagocytes from patients with systemic and discoid lupus erythematosus.

The digestion of bacterial DNA by peripheral blood monocytes was impaired both in patients with systemic lupus erythematosus (SLE) and discoid lupus erythematosus (DLE). The monocytes of these patients had both a small quantitative defect in the solubilization of DNA and a marked qualitative defect in the extent to which this DNA was degraded. In addition, neutrophils from patients with SLE released significantly less high molecular-weight DNA than control cells. Digestion of bacterial RNA and protein by phagocytes was not defective in either disease. The reduced digestion of DNA by phagocytes resulted in concomitantly larger amounts of high molecular-weight DNA remaining in these cells. Such sequestration of DNA may contribute to the persistence of fairly large DNA fragments in the tissue of patients with lupus erythematosus.