Increased production of an interleukin 1 (IL-1) inhibitor with fibroblast stimulating activity by mononuclear cells from patients with scleroderma.

We have previously demonstrated low IL-1 activity produced by peripheral blood mononuclear cells (PBMC) from patients with scleroderma (Sandborg et al., 1985) and the production of a 6-9 K IL-1 inhibitor by normal monocytes (Berman et al., 1986). To determine whether this inhibitor accounted for the low IL-1 activity present in scleroderma, the production of IL-1 and IL-1 inhibitor by PBMC from eight scleroderma patients was studied. Concentrated supernatants from 24 h cultures of unstimulated PBMC were fractionated on Sephacryl S-200 and tested for IL-1 and IL-1 inhibitor activity in the standard IL-1 thymocyte proliferation assay. In seven of eight patients, IL-1 inhibitor production was increased (average 3.3 X) compared to matched controls. IL-1 production was less than controls in six of eight patients. Partially purified preparations of the 6-9 K mol. wt IL-1 inhibitor were inhibitory to IL-1 induced thymocyte proliferation but stimulatory to fibroblast proliferation when purified by gel chromatography and chromatofocusing (pI 4.5-5.6). These data suggest that an IL-1 inhibitor with fibroblast stimulating activity is produced in higher amounts by PBMC from patients with scleroderma, and may contribute to the fibroblast proliferation and excessive collagen synthesis which is typical of this disease.