Reduced tumor growth after low-dose irradiation or immunization against blastic suppressor T cells.

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Abstract
Suppressor T cells are much more radiosensitive than other lymphoid cells. An attempt was made to reduce tumor growth by low-dose irradiation. Syngeneic DBA/2 mice received whole-body irradiation (150 rad; 1 rad = 0.01 J/kg) 6 days after [mouse Mastocytoma] P815 tumor cells inoculation. Tumor growth is significantly reduced in mildly irradiated mice. An attempt was made to reduce syngeneic tumor growth by raising immunity against suppressor T cells in 2 different systems. DBA/2 mice were immunized against splenic T cells collected after disappearance of cytotoxicity and then injected with P815 tumor cells. These mice develop a very high primary cytotoxicity against P815 cells. C57BL/6 mice were immunized against blastic suppressor T cells, before injection of [mouse methylcholanthrene-induced Sarcoma] T2 tumor cells. Some of these mice reject the tumor and others develop smaller tumors than control mice. These results could be explained by the induction of antiidiotypic activity directed against the immunological receptors of suppressor T lymphocytes, because immunization with blastic suppressor T cells from mice bearing the T2 tumor does not modify the growth of another tumor, T10.