Soluble interleukin 2 receptors in patients with sarcoidosis. Possible origin

We determined levels of soluble interleukin 2 receptors (IL-2R) in patients with sarcoidosis and further examined their origin. Thirty-nine patients with sarcoidosis and 18 healthy control subjects were studied. Soluble IL-2R levels in serum were significantly higher (p < 0.01) in sarcoidosis than in control subjects. In sarcoidosis, levels of soluble IL-2R in serum were significantly higher (p < 0.05) in patients with active disease than those with inactive disease and were significantly (p < 0.01) correlated with serum angiotensin-converting enzyme (ACE) levels. IL-2R expression on monocytes and alveolar macrophages (AMs) was significantly (p < 0.01) increased in patients with sarcoidosis as compared with control subjects. Soluble IL-2R levels in the supernatants of cultured monocytes and AMs were higher in patients with sarcoidosis than in control subjects. Those of cultured T lymphocytes obtained from peripheral blood and bronchoalveolar lavage fluid were detected in some patients with sarcoidosis, while undetected in control subjects. Furthermore, soluble IL-2R in serum was significantly correlated with soluble IL-2R in the supernatants of cultured monocytes and AMs (p < 0.01 and p < 0.05, respectively). These results demonstrate that soluble IL-2R in serum is a useful index of the disease activity of sarcoidosis and is mainly derived from monocytes and AMs.