INVIVO ANTI-TUMOR EFFECTS OF MONOCLONAL-ANTIBODIES WITH DIFFERENT IMMUNOGLOBULIN CLASSES

  • 1 January 1983
    • journal article
    • research article
    • Vol. 43  (10) , 4768-4773
Abstract
Monoclonal antibodies were produced against MM46, an MM antigen-positive, ascitic mouse mammary tumor of C3H/He mice, and 14 clones produced antibodies reactive with MM46, but not with an MM antigen-negative MM48 tumor. Among these 14 antibodies, 10 also reacted with lymph node cells of C3H.B6-Ly-6b, Ly-6.2 congenic mice. The antigen defined by the 10 antibodies was provisionally designated MM1, and the one defined by the other 4 was designated MM2. Further analysis of MM1 by antibody binding inhibition assay with 3H-labeled MM1-.gamma.2b-1 antibody revealed that 8 of the 10 antibodies and monoclonal anti-Ly-6.2 showed significant inhibition. Thus, there were > 2 antigenic determinants on MM1 antigen. The Ig class of 8 antibodies detecting the same antigenic determinant on MM1 was examined, and it covered major classes of mouse Ig (.mu., .gamma.1, .gamma.2a, .gamma.2b, .gamma.3 and .alpha.). Therefore, the in vivo effect against MM46 tumor cells by these antibodies was studied by a serological tumor neutralization assay. Tumor cells (4 .times. 105) were treated with antibodies and then injected s.c. into syngeneic C3H/He mice. Ten days later, the tumor was weighed. .gamma.2a antibody showed significant suppression of tumor growth, and .gamma.2b and .gamma.1 antibodies also revealed suppression. .mu., .gamma.3 and .alpha. antibodies did not show any significant effect on the tumor growth. To elucidate the mechanisms of tumor suppression by antibodies, the role of macrophages was studied by the antibody-dependent macrophage-mediated cytotoxicity test. In accordance with the in vivo tumor effects, .gamma.2a antibody showed 40-60% cytotoxicity up to a concentration of 1 .mu.g/ml, and .gamma.2b and .gamma.1 antibodies were also cytotoxic, although less so than .gamma.2a. Neither .mu. nor .alpha. antibody showed any significant cytotoxicity. .gamma.3 antibody showed very weak cytotoxicity against MM46 tumor cells. Thus, a good correlation was observed between the in vivo antitumor effects and in vitro antibody-dependent macrophage-mediated cytotoxicity activity with regard to each class of Ig, which suggested that macrophages may play an important role in the in vivo antitumor effect of the antibodies used.