IgM Antibody-Dependent Cell-Mediated Cytotoxicity in the Moloney Sarcoma Virus System: the Involvement of T and B Lymphocytes as Effector Cells

Abstract

Antibody-dependent cell-mediated cytotoxicity in the Moloney sarcoma virus (MSV) system was analyzed with respect to the subpopulations of effector cells involved in tumor target cell destruction when IgM was used as the sensitizing antibody. With unfractionated aera from animals that had undergone regression of primary MSV tumors it was found that macrophages did not contribute to the cytotoxicity induced by normal spleen cells that were syngeneic to the target cells. The IgM fraction of MSV regressor sera was found to induce cytotoxicity against the target cells by immunoadsorbent column-fractionated normal spleen cells, which were either depleted of T cells or B cells, according to the specificity of the columns. Immune IgM was also found to potentiate the activity of MSV regressor spleen cells that had been similarly fractionated. Furthermore, IgM antibody was found to induce cytotoxicity by normal spleen cells which had been depleted of either T or B cells by the appropriate antiserum (anti-T or anti-Ig) in the presence of complement and subsequent recovery of the viable cells by trypsinization, filtration, and washing. However, spleen cells treated with both anti-T and anti-Ig sera simultaneously in the presence of complement and subsequent recovery of viable cells, were not induced to be cytotoxic against the IgM-coated tumor target cells. Further support of the finding that IgM antibody could induce cytotoxicity by T cells was provided by an experiment showing the induction with IgM of cytotoxicity against the target cells by normal thymocytes.