Monocyte-mediated suppression of anti-DNA antibody production in healthy subjects

Monocyte-depleted mononuclear cells (MNC) from healthy subjects synthesized IgM-class antibody to single-stranded DNA (anti-ssDNA) at significantly higher levels than unfractionated MNC. The increased production of IgM anti-ssDNA by monocyte-depleted normal MNC was inhibited to a greater degree than total IgM by addition of supernatants from autologous monocytes. Moreover, supernatants obtained from normal monocytes cultured with indomethacin retained this suppressive effect on IgM anti-ssDNA antibody production, suggesting that prostaglandin E2 may not be involved in the suppression. These results indicate that B cells programmed to produce IgM anti-ssDNA are present in the normal B cell repertoire, but may be suppressed by monocytes or by a soluble factor (or factors) from the monocytes.