Sarcolemmal Coexpression of Intercellular Adhesion Molecule‐1 (ICAM‐1) and HLA‐DR in Inflammatory Myopathy

Abstract

This report concerns the immunohistochemical detection of the intercellular adhesion molecule‐1 (ICAM‐1), HLA‐ABC and HLA‐DR in consecutive cryostat sections of skeletal muscle biopsies from 38 patients with inflammatory myopathy. Among these were 12 cases of dermatomyositis, 22 cases of polymyositis, two cases each of inclusion body myositis and sarcoid myopathy. Specimens from eight cases of Duchenne muscular dystrophy, three cases each of alcoholic polyneuropathy and myotonic dystrophy, two cases of motor neuron disease, and three normal individuals were included for comparison. Sarcolemmal ICAM‐1 expression by undamaged muscle fibers was detected in 18/38 cases of inflammatory myopathy who had large numbers of endomysial inflammatory cells, but not in normals or patients with non‐inflammatory myopathy. Sarcolemmal immunostaining was more intense in the vicinity of the inflammatory cells. Some regenerating muscle fibers, irrespective of disease, expressed sarcoplasmic ICAM‐1. Sarcolemmal HLA‐ABC and HLA‐DR immunoreactivity was detected in undamaged muscle fibers of 37/38 and 18/38 cases of inflammatory myopathy, respectively. Sarcolemmal immunostaining for HLA‐DR was observed in cases with large amounts of endomysial inflammatory cells, and was stronger in muscle fibers that were in their vicinity. HLA‐DR and ICAM‐1 immunoreaction product deposits were generally colocalized in the sarcolemma of the same fibers. The specific sarcolemmal expression of ICAM‐1, and its colocalization with HLA‐DR may be important for the recognition of muscle fibers by invading inflammatory cells in inflammatory myopathy.