Immunoperoxidase EM localisation of cytoplasmic actin in cultured fibroblasts

Human smooth muscle autoantibody (SMA) of defined anti-actin specificity was tested by the indirect immunoperoxidase staining method on frozen sections of tissues and on cultured rat lung fibroblasts. The serum stained tissue sections and cultured fibroblasts in a pattern identical with that obtained by indirect immunofluorescence. Ultrastructural studies carried out on the immunoperoxidase stained cells showed that the long parallel filaments spanning the long axis of cultured fibroblasts seen by light microscopy correspond with the thick bundles of microfilaments.