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

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 alphaLeu-1 antibodies. In most instances, Leu-3a reactive T helper lymphocytes dominated over alphaLeu-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 provide basic data that are important for the understanding of inflammatory myopathy.