Immunological characteristics of the effector cells induced by a combination therapy with cyclophosphamide and allogeneic lymphocytes.

A significant inhibition of tumor growth was observed when sarcoma 180 (S180)-bearing ICR strain mice were treated by a combination therapy, with a low dose of cyclophosphamide (CY) and an inoculation of allogeneic lymphocytes collected from C57BL/6 mice. The growth-inhibitory effect was significantly increased by an inoculation of a relatively lower dose of allogeneic lymphocytes (1 x 10(5) cells) and CY. The effector cells induced in the mice treated with CY and allogeneic lymphocytes expressed the Lyt 1.2, Lyt 2.2, IL-2R antigens on their membrane surface and did not express the H2KbDb (donor H-2) antigen, and they showed a specific cytostatic activity against S180 cells. These results strongly suggested that a combination therapy with a low dose of CY with an inoculation of allogeneic lymphocytes augmented an induction of specific cytotoxic T lymphocytes in the tumor-bearing recipient mice.