Cytostatic effect of spleen cells of tumor-bearing mice on syngenetic tumor cells.

Spleen cell suspensions of methylcholanthrene-induced tumor-bearing mice were tested for their ability to inhibit tumor growth in vitro. The level of cytostasis was correlated with tumor growth and disappeared rapidly after surgical removal of the tumor. Pretreatment by anti-Thy 1-2 antiserum and complement, or by carbonyl iron and a magnet, showed that adherent, non-T-cells were the main effector cells of the cytostatic antitumor effect. Thymus cells suspensions from tubor-bearing mice were not effective in inhibiting tumor growth. This cytostatic effect was not tumor specific, inasmuch as the same spleen cell suspension inhibited growth of tumor cells of different origin.