Defective monocyte leukotaxis in sarcoidosis: possible relationship to a plasma factor.

Monocyte leukotactic function was studied in 25 untreated patients with histologically confirmed sarcoidosis. Monocyte leukotactic responses were significantly depressed (P less than 0.001), most strikingly in patients with stage I disease; however, the severity of the leukotactic defect did not correlate with duration, activity, or extrathoracic dissemination of disease. Preincubation of normal monocytes in sarcoid plasma, but not normal plasma, resulted in partial inhibition of leukotactic responsiveness. The leukotactic inhibition was not reversed by washing the cells after preincubation or by subsequent exposure to normal plasma. The inhibitory activity, which was found in all sarcoid plasma samples, was nondialyzable, was heat stable, and could be localized to the 25 to 35 per cent saturated ammonium sulfate fraction of plasma. Lesser amounts of similar inhibitory activity were detected in comparable fractions of normal plasma. A highly significant correlation between monocyte leukotactic responses and plasma leukotactic inhibitory activity was found in patients with sarcoidosis, suggesting an important in vivo modulatory nole for this substance.