Monocyte-mediated suppression of rheumatoid factor production in normal subjects.

The regulatory role of normal monocytes in the production of rheumatoid factor (RF) was investigated. Monocyte depletion from normal mononuclear cells (MNC) resulted in an elaboration of IgM RF in 18 of 20 subjects. The increased RF production was inhibited by the addition to the cultures of adherent cells or their culture supernatants. These observations demonstrate the suppressive role of normal monocytes in the production of RF. Supernatants obtained from normal monocytes cultured with indomethacin could suppress the RF production, suggesting that prostaglandin E2 may not be involved in the regulation of IgM RF production.