The role of vascular smooth muscle cells in experimental autoimmune vasculitis. I. The initiation of delayed type hypersensitivity angiitis.

The destruction of vascular smooth muscle cells (VSMCs) in autoimmune arteritis is a poorly understood phenomenon. For evaluation of the cellular interactions that may contribute to vasculitis, the immunobiology of VSMCs and lymphocytes was explored in vitro. Primary VSMC cultures were established, and the interaction of these cells (from normal or autoimmune mice) with lymphocytes was then assessed. Specifically, splenocytes from MRL/lpr or C3H mice were cocultivated with MRL/lpr or C3H VSMCs. Massive mononuclear cell clusters from normal and autoimmune mice enveloped MRL/lpr VSMCs, which culminated in the detachment of MRL/lpr VSMCs from the culture plate. In contrast, the interaction of SPs from either normal or autoimmune mice did not encompass or destroy normal VSMCs. Further investigation indicated that MRL/lpr, but not C3H, VSMCs spontaneously expressed Ia and released Il-1 like factor(s), which may be at least two mechanisms by which MRL/lpr VSMCs stimulate the in vitro mononuclear cell influx. As a result of these studies, a novel mechanism for the induction of mononuclear cell autoimmune vasculitis is proposed. VSMCs derived from autoimmune mice may stimulate a mononuclear inflammatory cell phlogistic response which culminates in VSMC autodestruction.