In vitro studies on the inhibitory effect of lymphoid cells. II. Antitumor activity of lymphoid cells from spontaneous mammary tumor-bearing mice on the autochthonous primary culture tumor cells

As a step in the elucidation of human cancer immunity we studied antitumor activity of lymphoid cells by conducting a series of cultures using the primary culture of cells from spontaneous mammary cancers from C3H and RIll mice mixed with autochthonous lymphoid cells, and obtained the following results. 1) With 24 mammary tumors obtained from 24 mammary cancer. bearing mice, we prepared 22 suspensions containing sufficient numbers of free tumor cells, and attempted primary culture with them. As a result we were able to attain satisfactory primary culture cells in 18 trials. 2) With each group of the 18 primary culture tumor cells we conducted mixed cultures with autochthonous lymphoid cells (mainly spleen cells) in proportion of 1 : 40, for 48 hours, and counted viable tumor cells after the culture. As a result it was found that in 11 trials the lymphoid cells showed antitumor activity. In the remaining 7 groups of lymphoid cells there could be observed no antitumor activity, but some of them showed tendency to slightly accelerate the growth of tumor cells. 3) On looking at the correlation between the antitumor activity of lymphoid cells and the ratio of tumor weight/body weight, it was revealed that the antitumor activity is greatest when the tumor is around 10% the body weight, and as the tumor grows larger, such antitumor activity disappears. From these results, it may be concluded that even in spontaneous mammary cancer of mouse, autochthonous lymphoid cells exhibit anti. tumor activity on indigenous tumor, and this seems to indicate that cell. mediated immunity has been established.