Release of interleukin-6 by alveolar macrophages in patients with sarcoidosis

Abstract

The supernatants from cultures of alveolar macrophages from 12 patients with sarcoidosis and 7 control subjects were assayed for interleukin-6 (IL-6) using an ELISA system. IL-6 was detectable without a stimulant in supernatants from all subjects with sarcoidosis and controls. However, the supernatants from 4 of 12 untreated patients with sarcoidosis contained significantly greater amounts of IL-6. When macrophages were stimulated by Propionibacterium acnes (P. acnes), the mean level of IL-6 in the supernatant of patients with sarcoidosis was 5.18 +/- 1.46 ng/ml, which was significantly higher than in controls (3.34 +/- 0.39) (p less than 0.05). Furthermore, in patients with sarcoidosis, the mean level of IL-6 in the supernatant was significantly correlated with the percentage of lymphocytes in bronchoalveolar lavage fluid (p less than 0.05), the level of interleukin-1 released by alveolar macrophages stimulated by P. acnes (p less than 0.05), and the phagocytic index of alveolar macrophages (p less than 0.05). The large amount of IL-6 in the supernatant after stimulation by LPS was measured in patients with sarcoidosis (24.49 +/- 13.36) and in controls (12.4 +/- 8.53), and there was no significant difference between patients with sarcoidosis and controls. Small amounts of IL-6 were detectable in bronchoalveolar fluid from only 2 of 26 patients with sarcoidosis; however, it was detected in none of 15 controls. It is suggested that the enhancement of IL-6 release by alveolar macrophages has a role in the activation of immune effector cells at sites of sarcoidosis.