title: Actin may be present on the lymphocyte surface.
abstract: Lymphocytes were assessed for the presence of surface actin and myosin by lactoperoxidase-catalyzed iodination and indirect immunofluorescence using antisera against purified pig skeletal muscle actin and pig smooth muscle myosin. Sodium dodecyl sulfate/polyacrylamide gel electrophoresis of 125I-labeled pig, mouse, and human B lymphocytes revealed an intense radioactive band of 43,000 molecular weight, whereas pig and mouse T lymphocytes gave a much less intense band. This band comigrated with actin, was nonglycosylated as judged by lack of binding to lentil lectin-Sepharose, was bound specifically by myosin fibers, and could be distinguished from a polypeptide of similar mobility derived from the major histocompatibility antigens. These results suggest that actin is present on the surface of B lymphocytes and, to a lesser extent, on T lymphocytes. Pig, mouse, and human Ig-bearing cells were stained by antiactin and antimyosin antisera, as judged by indirect immunofluorescence, whereas non-Ig-bearing cells were not stained. Antibody binding, however, was depleted by adsorbing the antisera with Ig-Sepharose. It was concluded that the immunofluorescence results are misleading and reflect the presence of antibodies that crossreact with Ig.
mesh_terms: D000199:Actins / Q000378:metabolism*; D001402:B-Lymphocytes / Q000648:ultrastructure; D002462:Cell Membrane / Q000378:metabolism; D007140:Immunoglobulin Fab Fragments; D008214:Lymphocytes / Q000648:ultrastructure*; D008565:Membrane Proteins / Q000378:metabolism*; D008970:Molecular Weight; D009218:Myosins / Q000378:metabolism; D013601:T-Lymphocytes / Q000648:ultrastructure
chemical_list: D000199:Actins; D007140:Immunoglobulin Fab Fragments; D008565:Membrane Proteins; D009218:Myosins