The suppressive effects of OK-432 and Ge-132 on 3-methylcholanthrene (MC) carcinogenesis have been confirmed. To clarify the mechamism of this suppression, we investigated the effects of anti-asialo GM1 antibody (AGM1), anti-thymocyte antibody (Thy) and carrageenan (CAR), which eliminate NK cells, T cells and macrophages, respectively, on the growth of MC induced sarcoma. The suppressive effect of Ge-132 in mice was abolished by prior AGM1, Thy or CAR treatment ; moreover, these compounds enhanced the development of tumors. In mice treated with OK-432, AGM1 or CAR enhanced the development of tumors, as well ; however, Thy treatment did not alter tumor incidence. Prior treatment with AGM1 reduced the percentage of large granular lymphocytes and NK activity, which were increased by OK-432 or Ge-132 treatment ; however, Thy or CAR did not alter these parameters.
These results indicate that NK cells and macrophages play an important role in the defense against MC induced sarcoma in OK-432-treated mice, while T cells as well as NK cells and macrophages do so in Ge-132-treated mice.