Mechanism of the damaging effect of dermatomyositis mononuclear cells on cultured human skin fibroblasts.

We further studied the mechanism of action of peripheral mononuclear cells (MNC) from patients with dermatomyositis (DM) to strikingly suppress fibroblast proliferation in vitro. Attachment of MNC to fibroblasts was closely related to the mechanism. Most of attached MNC were activated T lymphocytes. Conditioned medium alone did not show any effects on fibroblasts. T8 positive cells and monocytes were essential to elicit the effect. Study of 51Cr release demonstrated that DM MNC augmented cytolysis of fibroblasts. It might be concluded that DM MNC possess T lymphocyte mediated cytotoxicity on fibroblasts and this causes the inhibition of fibroblast proliferation.