Increased interleukin‐2 production in response to human type I collagen stimulation in patients with systemic sclerosis

Peripheral blood mononuclear cells (PBMC) from patients with systemic sclerosis (SSc) produced increased amounts of interleukin‐2 (IL‐2), in a dose‐dependent manner, in response to stimulation with human type I collagen, whereas PBMC from normal subjects did not. At a dose of 50 μg human type I collagen/106 PBMC, PBMC from SSc patients (n = 17) produced 8 times as much IL‐2 as did PBMC from 16 normal subjects (P < 0.005) and 3 times as much as did PBMC from a group of 13 rheumatoid arthritis patients (P < 0.05). In contrast, IL‐2 production by PBMC after nonspecific stimulation with the mitogen, phytohemagglutinin, did not differ among the SSc, rheumatoid arthritis, and normal control groups. Cell depletion experiments indicated that the IL‐2‐producing cells in SSc patients are CD4+. Thus, SSc patients have CD4 cells that are specifically sensitized to human type I collagen and can produce increased levels of IL‐2. Measurement of IL‐2 production stimulated by human type I collagen may be useful in evaluating disease activity, and further investigation of this process may contribute to the delineation of the pathogenesis of SSc.