Interleukin-1 production by mononuclear cells from patients with scleroderma.

Interleukin-1 (IL-1) production by peripheral blood mononuclear cells (PBMC) from patients with scleroderma and healthy controls was studied. Supernatants from unstimulated PBMC cultures from 10 of 13 patients with progressive systemic sclerosis (PSS) had significantly less IL-1 activity as measured by thymocyte proliferation than controls. IL-1 activity per monocyte/macrophage in both patients and controls was 10 times greater when PBMC were cultured at 10(5) cells/ml compared to 10(6) cells/ml. Five-fold dilution of supernatants from PBMC cultured at 10(6) cells/ml revealed more IL-1 activity than undiluted supernatant and addition of indomethacin increased IL-1 activity primarily of the undiluted supernatant. The results show that IL-1 activity from crude PBMC supernatants from PSS patients is low and may be regulated by non-dialysable inhibitors produced by PBMC and/or cell interactions.