title: Effect of concanavalin A on the killing of tumor cells by antibody and complement.
abstract: Concanavalin A (Con A) was found to inhibit the killing of antibody-sensitized line-1 tumor cells (TA) by guinea pig complement (GPC) but not by human complement (HuC). Other plant lectins (wheat germ, leucoagglutinin, and pokeweed mitogen) were also tested but Con A was the only lectin found to inhibit antibody-GPC-mediated killing. The inhibitory effect of Con A was observed when the GPC was mixed with Con A or when the antibody-sensitized cells were pretreated with Con A (TA-Con A) before the addition of GPC. The effect could be reversed by treatment of such cells with alpha-D-methylglucopyranoside or by incubation at 37 degrees C for approximately 2 hr. Con A appeared to act by preventing the binding of the first component of GPC (GPC1) to antibody-sensitized tumor cells. Differences in the binding of the first component of HuC (HuC1) and GPC1 to TA-Con A suggested that a difference in the binding site for HuC1 and GPC1 might exist. There was no difference in the number of GPC1 molecules fixed to antibody-sensitized sheep erythrocytes (EA) or EA treated with Con A in experiments using the same antibody as used with the tumor cells and the same Con A preparation. It would consequently appear that the inhibitory effect of Con A on the binding of GPC1 to TA is not due solely to an interaction of Con A with the antibody.
mesh_terms: D000818:Animals; D000906:Antibodies; D001665:Binding Sites; D006528:Carcinoma, Hepatocellular / Q000276:immunology*; D002462:Cell Membrane / Q000276:immunology; D003172:Complement C1; D003168:Complement Fixation Tests; D003165:Complement System Proteins; D003208:Concanavalin A / Q000494:pharmacology*; D003601:Cytotoxicity Tests, Immunologic; D005577:Forssman Antigen; D006168:Guinea Pigs; D008113:Liver Neoplasms / Q000276:immunology*; D009374:Neoplasms, Experimental / Q000276:immunology; D013045:Species Specificity
chemical_list: D000906:Antibodies; D003172:Complement C1; D003208:Concanavalin A; D003165:Complement System Proteins; D005577:Forssman Antigen