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Characteristics of the Immature Cells Involved in T Cell-Mediated Enhancement of Syngeneic Tumor Growth¹

From the Department of Cell Biology, The Weizmann Institute of Science, Rehovot, Israel

Abstract

Enhancement of tumor growth was observed when nonsensitized thymocytes were injected together with tumor cells into syngeneic mice, although this tumor enhancement was less pronounced than that caused by tumor-sensitized T lymphocytes. The cells within the thymus which are responsible for this tumor enhancement were found to be rapidly dividing and to be absent from the thymus 1 day after cortisone administration. At a longer time interval the cortisone-depleted thymus was repopulated by dividing cells which exhibited tumor-enhancing reactivity. The characteristics of these cells suggest that they are in the early stages of thymic processing. The enhancing thymocytes were sensitive to treatment with the thymic humoral factor which functions in T cell maturation, and their enhancing activity was cancelled by such treatment. These results are compatible with our hypothesis that exposure of immature T cells to a tumor stimulus may lead to tumor enhancement whereas interaction between mature T lymphocytes and tumor cells may be required for tumor inhibition.

Footnotes

¹ This work was supported by the Yehudit Segal Fund for Cancer Research, Jerusalem.

² Leopold and Margarete Schwarz Memorial Cancer Research Fellow.