T-cell recruitment from the thymus to the spleen in tumor-bearing mice. II. Functional characteristics of recruited T-cells.

The effect of prostaglandin E2 (PGE2) on characteristics of splenic T-cells in tumor-bearing mice (TBM) was studied from the viewpoint of PGE2-mediated cell-recruitment system from the thymus to the spleen. The splenic T-cells of TBM enhanced tumor growth. In the TBM, the total number of thymocytes decreased, and the number of splenic T-cells concurrently increased. In adult thymectomized tumor bearers, these tumor growth-enhancing T-cells were absent in the spleen, and the number of splenic T-cells remained unchanged. Such suppressor T-cells in the spleens of TBM may relate to recruitment of immature T-cells from the thymus. The levels of PGE2 in the plasma were depressed in the TBM. Replenishment by exogenous PGE2 prevented both an increase in splenic T-cell population and an augmented generation of T-cells that had an enhancing effect on tumor growth. Our findings show that a low level of PGE2 induced the T-cell recruitment from the thymus to the spleen and that such recruited cells led to an acceleration of tumor growth.