Kinetics of thymus- and bone marrow-derived lymphocytes in rats during tumor growth

The kinetics of T and B lymphocytes were studied in the spleen, the lymph nodes, peripheral blood and the thymus of tumor-bearing rats in a time dependence following tumor transplantation with varying doses of allogeneic tumor cells. The dose of the transplanted tumor cells proved to be a limiting factor in the altered proportions of T and B cells in the various phases of immunological response of the tumorous host. A lower dose of tumor cells induced but a nonsignificant decline in the numbers of T lymphocytes in correlation with tumor growth and the tumor rejected within 19 days. A high dose of tumor cells caused an evident exhaustion of T cells in all the lymphoid organs followed (excepting the thymus), and the tumor was not rejected even by the end of the experiment. Evidently, the presence of tumor cells did not affect the B cell pool. The results are interpreted in the sense of a functional heterogeneity of the various subpopulations of T lymphocytes. The reactivity and responsibility of these subpopulations in the phase of tumor growth and its rejection is discussed.