MAJOR HISTOCOMPATIBILITY COMPLEX EXPRESSION IN MUSCLE OF RATS WITH GRAFT-VERSUS-HOST DISEASE

Immunohistochemical examination of rat skeletal muscle during graft-ve rsus-host disease (GVHD), a systemic immune reaction, was performed to investigate specific immune reactivities focusing on major histocompa tibility complex (MHC) expression and inflammatory cell infiltration o f skeletal muscle during a systemic immune reaction. MHC class II expr ession and inflammatory cell infiltration did not increase. MHC class I was expressed along the contour of muscle fibres, and most strongly expressed by the cells which were distributed throughout the endomysiu m and perimysium. Seventy-six percent of these MHC class I+ cells carr ied endothelial cell-markers, while 24% of them did not. The latter ce lls were revealed not to be inflammatory cells such as lymphocytes, gr anulocytes or macrophages when examined by immunostaining using severa l exudate-cell markers. Neither were they myosatellite cells because t hey were located outside the basement membrane. These results may be u seful for considering animal models of inflammatory myopathies such as polymyositis and dermatomyositis.