Cytotoxic Isoantibodies and Immunologic Enhancement in Mice. ∗

Abstract

Summary

1. Cytotoxic isoantibodies and hemagglutinins are stimulated in response to H-2 isoantigenic differences between graft and host in mice. 2. This study offers data correlating cytotoxic isoantibody and immunological enhancement. 3. The mechanism of immunological enhancement has been shown to be associated with peripheral as well as central inhibition of transplantation immunity and allograft rejection. 4. Antisera produced by immunization of TS mice with antibody-coated C3H_f/He tumor cells (incubated with immune serum) had a hemagglutination titer of 1:128. They were more potent in cytotoxic and especially cytolytic effects against tumor cells in vitro than were anti-sera, of 1:256 hemagglutination titer, to untreated tumor cells. The cytotoxic activity (comparison of antiserum to antibody-coated tumor cells to antiserum to uncoated tumor cells) was most remarkable in the 1:100 tube dilution. 5. The increased cytotoxic activity induced by antibody-coated tumor cells was postulated to be a result of antibody stimulation by freed competitor antigens termed cytotoxinogens. 6. Enhancement of antibody-coated tumor cells which occurred is in agreement with the concept that immunological enhancement does not depend upon resistance of tumor cells to immune serum.