Sarcoma 180(S.180) tumor cells were transplanted to the peritoneal cavity and subcutaneous tissue of the inguinal region of mice, and then, Mycoplasma hominis were inculated into the peritoneal cavity of the mice 7 times. Inhibitory effect of
tumor
growth, effect of life prolongation, and changes of T cell subsets in the spleen, and changes of phagocytic rate of the macrophages were examined. The growth of S. 180 in the peritoneal cavity was suppressed and the survival rate of those mice
was
increased in the group of mice inoculated with M. hominis after transplantation with S. 180. The growth of tumor was suppressed and the suppression rate of the tumor growth was 43.6% in the group inoculated with M. hominis after transplantation
with S.
180. In the spleen, the number of total T cells and T helper cells of each study groups was not different from that of the control group. In the group, however, inoculated with M. hominis alone and the group preinoculated with M. hominis 7 times
before
transplantaton with S. 180, T suppresor cells were decreased in number. In the spleen, in both group transplanted with S. 180, and inoculated with M. hominis after 7 days, and the group transplanted with S. 180 after M. hominis was inoculated 7
times,
the number of NK cells was increased. In other groups, however, the number of NK cells was decreased. The rate of phagocytosis of peritoneal macrophage from the mice inoculated with M. hominis was increased. The titers of serum antibody against
M.
hominis in the group of mice inoculated with M. hominis at different times after transplantation with S. 180 were increased from 320 to 1280 folds.
All above results suggest that the tumor growth was inhibited by inoculation with M. hominis in the mice transplanted with S. 180., and propose that the tumor growth inhibition is not caused by the changes of number of T cell subsets but by
number
of NK
cells and activity of macrophages.
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