ANTIBODY-INDUCED MODULATION AND SHEDDING OF MAMMARY-TUMOR VIRUS-ANTIGENS ON SURFACES OF GR ASCITES LEUKEMIA-CELLS AS COMPARED WITH NORMAL ANTIGENS

The distribution, antibody-induced redistribution, and shedding of murine mammary tumor virus (MuMTV) antigens on the surfaces of GR mouse ascites leukemia (GRSL) cells were studied by the immunoferritin technique and compared with the same activities of Thy 1.2. and H-2.8 antigens. MuMTV antigens were redistributed easily and then shed from cell surface. H-2.8 antigen moved easily and probably was partially released from the plasma membrane and Thy 1.2 antigen moved slowly and was somewhat interiorized. The complement-dependent cytotoxicity test was used to study the possibility of antigenic modulation for these cell surface antigens. MuMTV antigens from the surface of the GRSL cells could be modulated by preincubation with anti-MuMTV serum, in contrast to H-2.8 and Thy 1.2 antigens. The results obtained with the immunoferritin technique and cytotoxicity test correlated well and suggested that the shedding of MuMTV antigens from the cell surfaces may occur in vivo, providing the tumor a way to escape from the immune defense of the host. Thy 1.2 and H-2.8 antigens were present on the envelope of B and C particles, which suggested that these viruses do not select a Thy 1.2- or H-2.8-negative area of the GRSL cell surface as a maturation site.