Experimental allergic myositis: ultrastructural, histochemical, immunological and immunohistochemical studies.

The quadriceps femoris muscles of experimental allergic myositis, in strain 13 guinea pigs immunised with rabbit myosin B fraction, were subjected to histochemical, immunohistochemical and electron microscopic studies. They demonstrated a variety of degenerative changes of muscle fibres, infiltration of lymphocytes and macrophages along with deposition of immunoglobulin G (IgG) and complement factor 3 on the surface of the muscle fibres. One third of the infiltrating cells were macrophages with acid phosphatase activity in the cytoplasm. The serum IgG of the model had an affinity for the surface of normal guinea pig muscle fibres and for thick filaments and other organelles. Its affinity for the heavy and light chains of myosin, actin, troponin T and for other proteins was shown by the immunoblotting method combined with one- and two-dimensional electrophoreses.