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.

Thymus-dependent increase in number of T cells in parathymic lymph nodes induced by the biscoclaurine alkaloid, cepharanthine.

In mice treated with cepharanthine (Cepha), a biscoclaurine alkaloid, the number of T cells was increased in the parathymic lymph nodes (PtLNs) which are considered to be the specialized lymph nodes in local differentiation of T cells. Such PtLN cells exhibited augmented proliferative responses to T cell mitogens and exogenous interleukin 2 (IL 2) and showed a great ability to produce IL2, which suggests an increase in mature T cells in the PtLN. However, such increases in the number of T cells and in the mitogen response were not observed in adult thymectomized mice. A low level of plasma prostaglandin E2 (PGE2) was observed in Cepha-treated mice. Replenishment of the PGE2 in such mice with exogenous PGE2 prevented the increase in T cells in the PtLN. These results suggest that the migration of mature T cells from the thymus to PtLN is increased by Cepha and that Cepha is able to regulate their traffic by a prostaglandin-mediated system.