Defective immunoglobulin secretion in response to pokeweed mitogen in sarcoidosis.

We studied in vitro immunoregulation of immunoglobulin (Ig) secretion in 21 patients with sarcoidosis. While peripheral blood mononuclear cells from normal individuals responded to pokeweed mitogen with a 10-fold or greater increment in Ig-secreting cells, cells from sarcoid patients failed to respond to pokeweed mitogen at any concentration employed (P less than 0.001, Student's t-test, two-tailed). More monocytes were found in sarcoid mononuclear cell preparations (44.8 +/- 2.0% vs 30.4 +/- 1.4% in normal donors, P less than 0.001), but removal of monocytes improved the response to pokeweed mitogen in only four patients. Mononuclear cells from seven of 19 patients suppressed Ig secretion in co-cultures with normal donor cells. Patients exhibiting excessive suppressor cell function were older, with longer standing and less clinically active disease than non-suppressing patients. Monocyte removal reversed the suppression in only four of the suppressor patients, but excessive suppressor monocyte function was later demonstrated in two sarcoid patients whose cells initially did not suppress Ig secretion when cultured with normal cells. While the immunological defects in sarcoidosis may be complex, heterogenous, and dynamic, these data suggest that suppressor monocytes, when present in sarcoidosis, may have developed secondarily.