MHC CLASS-I, MHC CLASS-II AND INTERCELLULAR-ADHESION MOLECULE-1 (ICAM-1) EXPRESSION IN INFLAMMATORY MYOPATHIES

We investigated the relationship between the MHC-I, MHC-II and interce llular adhesion molecule-1 (ICAM-1) expression on myofibres and the pr esence of inflammatory cells in muscle specimens of 18 patients with i nflammatory myopathies (nine polymyositis, seven dermatomyositis, two inclusion body myositis). We observed MHC-I expression in muscle fibre s, infiltrating mononuclear cells and endothelial cells in every speci men. In seven patients, some muscle fibres were MHC-II-positive for th e DR antigen, while the DP and DQ antigens were absent. ICAM-1 express ion, detected in seven patients, was found in clusters of myofibres, a ssociated with a marked MHC-I positivity and a widespread mononuclear infiltration. Most of the ICAM-1-positive fibres were regenerating fib res. Furthermore, some fibres expressed both ICAM-1 and DR antigens ne ar infiltrating cells. This finding could support the hypothesis that myofibres may themselves be the site of autosensitization.