Formation of Cytoxic Antibody against Leukemias Induced by Friend Virus.

A specific antigenic component in mouse leukemias induced by Friend virus has been demonstrated by cytotoxic tests in vitro. Serum from mice of several inbred strains immunized with histoincompatible Friend leukemia tissue contained antibody that was cytotoxic in vitro for leukemia cells induced by Friend virus in the strains providing the immune serum. Unexpectedly, a high proportion of mice from strains that are highly susceptible to leukemogenesis by Friend virus did not develop leukemia after immunization as adults with incompatible viable Friend leukemia cells or with large amounts of infective filtrate. Cytotoxic sera could therefore be prepared in mice of both resistant and susceptible strains. By direct cytotoxic tests, and also by absorp tion studies, the Friend and Rauscher viruses appeared to induce the same antigenic change in the spleen cells of infected animals. A similar antigen has not been found in a variety of normal and leukemia tissues, including leukemias induced by the Passage A Gross virus.