A fluorescence study on the mobility of surface antigens of untreated tumor cells and of tumor cells undergoing cell-mediated lysis.
Heterologous (rabbit) antibodies were raised against murine P-815 mastocytoma cells of DBA/2 origin. Antisera and IgG preparations were highly cytotoxic, whereas Fab fragments thereof lost all activity. Fab fragments also showed a much lower avidity than IgG, both for tumor and normal DBA/2 and C57 spleen cells as measured by the release of iodinated Fab and IgG. Both preparations bound specifically to P-815 cells since they were capable of inhibiting T cell-mediated target cell lysis. The binding of IgG and monovalent Fab fragments was studied by fluorescence. Rhodamine-coupled IgG bound homogeneously in the cold and quickly formed patches upon warming but did not form caps even after prolonged incubation at 37 degrees C. Rhodamine-coupled Fab fragments also bound homogeneously. Their distribution was unaltered after incubation at 37 degrees C even when tumor cells formed uropod-like tails. Fab fragments, however, could be induced to cap with a second and third antibody layer. P-815 cells labeled with rhodamine-coupled Fab fragments were incubated with cytolytic T cells (CTL). The conjugates formed between CTL and fluorescent target cells were observed. No gross redistribution of surface antigens on target cells was observed even at late stages of the lytic process. CTL, therefore, do not seem to operate via a redistribution of surface antigens.
D000818:Animals; D000951:Antigens, Neoplasm / Q000032:analysis*; D000954:Antigens, Surface / Q000032:analysis*; D003602:Cytotoxicity, Immunologic; D007074:Immunoglobulin G; D012515:Mast-Cell Sarcoma / Q000276:immunology; D051379:Mice; D009374:Neoplasms, Experimental / Q000276:immunology; D011817:Rabbits; D013154:Spleen / Q000276:immunology; D013601:T-Lymphocytes
D000951:Antigens, Neoplasm; D000954:Antigens, Surface; D007074:Immunoglobulin G