HLA-DR expression, T lymphocyte phenotypes, OKM1 and OKT9 reactive cells in inflammatory myopathy

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Abstract
Frozen muscle biopsy sections from 13 patients with inflammatory myopathy and from four healthy volunteers were characterized with a double immunohistochemical staining technique, utilizing a panel of antisera to cell surface antigens. The technique enables simultaneous visualization of HLA‐DR reactive cells and other cell types, i.e., T lymphocytes. In inflammatory myopathy, large numbers of HLA‐DR reactive “macrophage/dendritic” cells were shown. Almost all other inflammatory cells and endothelial cells also expressed HLA‐DR, as did the sarcolemma in the vicinity of inflammatory foci. Large numbers of T lymphocytes were detected by αLeu‐1 antibodies. In most instances, Leu‐3a reactive T “helper” lymphocytes dominated over αLeu‐2a reactive T “suppressor/cytotoxic” lymphocytes. Many T lymphocytes of both phenotypes appeared in close contact with HLA‐DR expressing non‐T cells. OKM1 and OKT9 antibodies, labeling macrophages and “proliferating” cells, respectively, were common among inflammatory cells. The findings provides basic data that are important for the understanding of inflammatory myopathy.