Abnormalities in the content of nucleic acids of peripheral blood mononuclear cells from patients with systemic lupus erythematosus.

We have completed 59 cytofluorographic studies of DNA/RNA content in acridine orange-stained peripheral blood mononuclear cells from 44 patients with systemic lupus erythematosus, most of whom received no medications. Most such cells were in resting phases of the cell cycle, particularly those from patients with inactive disease. Nine patients with systemic lupus erythematosus had increased percentages of these cells in the synthesis and postsynthesis phases of the cell cycle; the B lymphocyte had a greatest proportions of activated cells. In 11 patients, we found that cells, particularly T lymphocytes, had increased RNA content without a proportional increase in DNA. This DNA block occurred primarily in patients with serum antibodies to DNA and it could be reproduced in normal mitogen-stimulated mononuclear cells incubated in heat-inactivated sera from patients with systemic lupus erythematosus whose own cells showed abnormalities of DNA/RNA content or in purified native DNA antibody. The DNA blocking potential of the DNA antibody was dependent on its Fc portion and on the presence of Fc receptors on T cells. Thus, saturation of Fc receptors by pretreatment with aggregated IgG or incubation with the whole antibody in the cold prevented the DNA block, indicating that it was an active process.