Correlation of in Vivo and in Vitro Immune Reactions Against the Intradermally Developing P-815 Mastocytoma in the Syngeneic Mouse

Abstract

Although the highly malignant P-815 mastocytoma is fatal to syngeneic hosts when as few aauthor00 cells are injected intraperitoneally, growth of this tumor can be inhibited or suppressed when such cells are injected intradermally. The optimum cell number for transient growth inhibition or spontaneous rejection was found to be 10 4-10 5 cells. The phase of regression was perceptible by days 10-12. During tumor growth concomitant immunity developed as demonstrated by the suppression of a second tumor cell injection. The peak of the concomitant immunity was found between days 10-12. Immunity was adoptively transferable with spleen-or better lymph node cells from tumor bearing animals on days 10-12. Tumor regression and the development of concomitant immunity were paralleled by the appearance of lymphoid cells which in vitro kill the tumor target cells. Interestingly, lymphocytes from the draining lymph node were found to have a ten times higher killing capacity than lymphocytes from the spleen, whereas cells from the non-draining lymph nodes were not cytotoxic. Abrogation of cytotoxicity after treatment of effector cells with anti Thy-1.2 antibody and complement demonstrated that cytotoxicity was due to T cells. The suppression of the regression phase in vivo by treatment of the animals with Cyclosporin A suggested that T cells were also effective in vivo. However, despite the pronounced immunity in some animals, no definite immune reaction, either in vivo or in vitro, was observed in others.