Activation of T lymphocytes by syngeneic murine intestinal smooth muscle cells

Intestinal smooth muscle cells (ISMCs) express major histocompatibility complex II (MCH II) and intercellular adhesion molecule 1 (ICAM-1) after exposure to interferon gamma (IFN-gamma). T lymphocytes invade the intestinal musculature during Crohn's disease or pseudoobstruction. The aim of this study was to determine whether ISMCs activate syngeneic T cells via MHC II and ICAM-1.

Cultured murine ISMCs were exposed to IFN-gamma for 72 hours and analyzed for Mac-1 (CD11B CD18) antigen, MHC II, and ICAM-1 expression using enzyme-linked immunosorbent assay and fluorescence-activated cell sorter scan. T lymphocytes from mesenteric lymph nodes of ovalbumin-sensitized mice were examined for their ability to proliferate after coculture with IFN-gamma-pretreated and ovalbumin-pretreated ISMCs using [3H]thymidine incorporation.

ISMCs expressed smooth muscle alpha-actin before and after IFN-gamma exposure. No macrophages were identified in these cultures. Exposure to IFN-gamma and ovalbumin for 72 hours induced MHC II and ICAM-1 expression; these treated ISMCs induced T-cell proliferation, whereas untreated ISMCs did not. T-cell proliferation was markedly enhanced by adding interleukin 2 and was blocked by antibodies against MHC II and ICAM-1.

ISMCs activate T lymphocytes in an MHC II-linked manner and thus possess the ability to modulate immune function in the gut.