Allograft cytotoxicity: critical role for adherent T cells in effector mechanism of the peritoneal population.

C57BL10 (H-2^b) mice were immunized intraperitoneally with the P815 (H-2^d) mastocytoma. Cytolytic activity measured by the ⁵¹Cr-release assay and cytostatic activity measured by ¹²⁵I-labeled UdR incorporation were assessed in the peritoneal population 12 days after tumor inoculation. Both antitumor effects were immunologically specific and totally dependent on T cells. In the adherent fraction of the immune peritoneal population cytostasis was quantitatively of greater significance than cytolysis. Despite the predominance of macrophages as identified functionally and morphologically, cytostatic activity of the adherent fraction appeared to depend on a small proportion (<13%) of adherent T cells. In addition, a macrophage of highly characteristic morphology was identified in the adherent population. This cell was relatively large and packed with large osmophilic granules.