Increased interleukin 6 production by bronchoalveolar lavage cells in patients with active sarcoidosis

Alveolitis of sarcoidosis is characterized by activated alveolar macrophages (AMs) and T cells. The mediators interleukin-1 (IL-1) and interleukin 6 (IL-6) released by AMs represent essential factors for the progression of the T cells in the cell cycle. The role of IL-1 in pulmonary sarcoidosis has previously been studied; however, the relevance of other mediators (i.e. IL-6) has not yet been evaluated. We measured the spontaneous and lipopolysaccharide (LPS)-induced release of IL-6 and tumor necrosis factor alpha (TNF alpha) by bronchoalveolar lavage cells (BAL) and peripheral blood mononuclear cells (PBMNC) in 6 control subjects (group A) and in 15 patients with sarcoidosis, 10 with active (group B), 5 with inactive disease (group C). IL-6 as well as TNF alpha were spontaneously released by BAL cells of the active group in significantly greater amounts compared to both other groups; IL-6: A, 165.5 pg/ml/24 hr/10(6) cells (range, 0-604), B, 946 (0-2467), C, 16.6 (0-83); TNF alpha: A, 162 pg/ml/24 hr/10(6) cells (0-523), B, 803 (100-17352), C, 100 (0-379). In all groups autologous PBMNC proved to be quiescent, releasing only baseline levels of the cytokines tested. After stimulation with LPS all these cells released great quantities of IL-6 and TNF alpha. In active disease a positive correlation between IL-6 and TNF alpha release was observed (r = 0.77, p < 0.02). The present study documents that in active sarcoidosis the spontaneous release of IL-6 by BAL cells parallels the spontaneous release of TNF alpha. IL-6 is capable of initiating the proliferation and activation of T cells in the lung.