Accessory cell activity of monocytes in anti-DNA antibody production in systemic lupus erythematosus.

Depletion of monocytes from peripheral blood mononuclear cells of patients with systemic lupus erythematosus (SLE) resulted in a decreased anti-DNA antibody synthesis in vitro. The addition of monocytes restored the response by lymphocytes and the maximum response in the presence of 2.5-8% of monocytes, whereas greater than 15% of monocytes caused rather decreased antibody responses. In order to further evaluate the role of monocytes on an anti-DNA antibody synthesis, we designated an accessory cell index, based on reconstitution experiments using isologous SLE lymphocytes, and compared it in active or inactive SLE and controls. The studies revealed that active SLE monocytes enhanced spontaneously occurring anti-DNA antibody synthesis by SLE lymphocytes. These results indicate that SLE monocytes actively participate in spontaneously occurring anti-DNA autoantibody synthesis in humans.