Lymphocyte subsets in muscle biopsies of human T-lymphotropic virus type I carriers with polymyositis.

Recent epidemiologic studies have shown that human T-lymphotropic virus type I (HTLV-I) is associated with polymyositis. To clarify the histological features of HTLV-I positive polymyositis, we studied muscle tissue from two groups of patients with polymyositis, those seropositive for HTLV-I (5 patients) and those seronegative (5 patients). We examined the lymphocyte subsets in muscle biopsies using monoclonal antibodies. In the endomysium, a variable number of T-lymphocytes and macrophages and a smaller proportion of B-lymphocytes were found in both groups. In both HTLV-I positive and negative patients a variable number of T-lymphocytes and macrophages, with a smaller number of B-lymphocytes, were found in the perimysium. As a whole, the T-lymphocytes were predominantly of the helper/inducer phenotype in both groups. We failed to find any specific phenotype distribution among T-cells infiltrating the muscle of HTLV-I carriers with polymyositis.