Physicochemical and Morphological Characterization of a New Allotransplantable Mammary Carcinoma Ascites Subline, TA3-St/ticol/-A

The TA3-St/ticol ascites cell (I), immunoselected from the strain-specific TA3-St mammary carcinoma ascites cell of the strain A mouse for decreased H-2' antibody-binding capacity, underwent a spontaneous transition in vivo to a new cell line, TA3-St/ticol/-A (II). Line II was more allotransplantable than was the parental line (line I), and its absorptive capacity for anti-H-2a antibody was manyfold less than line I. Disruption of line II cells by lyophilization did not increase the absorptive capacity, in contrast to its marked enhancement in the TA3-Ha ascites cell under similar conditions. An explanation for the enhanced allotransplantability of line II may be related to either a loss of H-2a antigens or altered macromolecular structures at the cell surface: sialic acid, consisting of 93% N-glycolylneuraminic add for line II and 9% for line I; altered chemical structures of cell surface glycoproteins, particularly a high-molecular-weight glycoprotein present in much greater proportion in line II than in line I; a macromolecular complex released by a protease from line I, but not line II; and I being agglutinable by concanavalin A, but not line II. Electron microscopy showed line II to be more pleomorphic and less rounded than was line I. Under high-resolution electron microscopy, the cell surfaces of both allotransplantable cells, lines II and I, exhibited thin filamentous material, material not observed at the surface of the nonallotransplantable TA3-St ascites cell.