Reaction of human smooth muscle autoantibody with foetal glial cells and their precursors.

Tissue culture monolayers of dissociated human and rat embryonic brains were examined by indirect immunoflurescence with human serum containing smooth muscle antibody. Flat, epithelioid cells showed staining of a fine, filamentous network in the cell body while multipolar cells showed diffuse cytoplasmic fluorescence of the cell body and processes. Both cell types were identified as glial cells by silver stains. Specificity of the immunofluorescent staining reaction was established by failure to obtain staining with normal serum, with smooth muscle antibody serum neutralized by homogenates of smooth muscle or by extracts contining actin-like protein derived from smooth muscle. Reacitivity of of embryonic glial cells with smooth muscle antibody indicates the presence of actin-like proteins which are probably located in cytoplasmic microfilaments.