Immunocytochemical localization of immunoglobulins in the inflammatory lesions of polymyositis.

Biopsy material from the muscles of 40 patients with either polymyositis or dermatomyositis was examined with the immunoperoxidase method to compare the distribution of immunoglobulin (Ig)-containing cells in the inflammatory infiltrates and elsewhere in the muscle tissue. Large numbers of IgG-positive and occasional IgM-positive cells were found in the infiltrates in 23 of these biopsies in contrast to the rather sparse representation of plasma cells. It is suggested that the Ig-containing cells may either represent local B-cell differentiation and proliferation or that the cells are involved in antibody-dependent cell-mediated tissue damage.