title: Cell surface alpha 1-protease inhibitor on human peripheral mononuclear cells in culture.
abstract: We have studied expression of alpha 1-protease inhibitor (alpha 1-PI) by human mononuclear cells. alpha 1-PI was detected on 50% of freshly isolated peripheral mononuclear cells. Unless a proliferative stimulus was provided, alpha 1-PI subsequently disappeared from the cell surfaces. Plant mitogens, periodate, neuraminidase-galactose oxidase, or allogeneic cells all were effective stimuli of alpha 1-PI expression. Concanavalin A stimulated de novo synthesis of alpha 1-PI in cell cultures containing both lymphocytes and mononuclear phagocytes, and alpha 1-PI simultaneously appeared on surfaces of activated lymphocytes. Inhibition of protein synthesis by cycloheximide or monocyte depletion abolished de novo alpha 1-PI synthesis, but only monocyte depletion inhibited alpha 1-PI expression. Lymphocytes, but not monocytes, displayed saturable binding of radioiodinated alpha 1-PI. The data are consistent with the interpretation that human mononuclear phagocytes synthesize and secrete alpha 1-PI. When protein synthesis is inhibited, mitogenic stimuli may provoke release of previously synthesized alpha 1-PI from mononuclear phagocytes. Secreted alpha 1-PI then may bind to specific lymphocyte cell surface receptors. This pattern of alpha 1-PI synthesis, secretion, binding, and expression on lymphoid cell surfaces appears to be a common characteristic of many immunologic reactions in vitro.
mesh_terms: D001402:B-Lymphocytes / Q000032:analysis; D001798:Blood Proteins / Q000032:analysis* / Q000235:genetics / Q000276:immunology; D002462:Cell Membrane / Q000032:analysis; D002469:Cell Separation; D002478:Cells, Cultured; D000939:Epitopes; D006801:Humans; D007700:Kinetics; D008213:Lymphocyte Activation; D008214:Lymphocytes / Q000032:analysis* / Q000378:metabolism; D008264:Macrophages / Q000032:analysis; D009000:Monocytes / Q000032:analysis*; D011971:Receptors, Immunologic / Q000032:analysis; D013601:T-Lymphocytes / Q000032:analysis; D000515:alpha 1-Antitrypsin
chemical_list: D001798:Blood Proteins; D000939:Epitopes; D011971:Receptors, Immunologic; D000515:alpha 1-Antitrypsin