Involvement of T cells in the recall of Salmonella-induced resistance to tumour.

Immunization of mice with Salmonella enteritidis 11RX (11RX) induces resistance to tumour growth in these animals. The degree and duration of resistance is dependent on the routes used for immunization and tumour challenge. When resistance to tumour growth has declined, it can be recalled using various 11RX antigen preparations. In the present study we have shown that the ability to recall resistance to i.p. challenge with 131I-labelled Ehrlich ascites tumour cells could be transferred to normal mice by i.p. injection of an antigen preparation of 11RX mixed with spleen cells from 11RX-immunized mice. The active cells in this test were apparently sensitized T cells, since spleen cells from normal mice were not effective and the activity of immune spleen cells could be markedly reduced by removing theta antigen-bearing cells but not by removing glass-adherent cells. The induction of in vivo cytotoxicity appeared to depend on the involvement of radiation-sensitive cells derived from the non-immunized recipients, since recall of resistance to tumour challenge was reduced when irradiated mice were used as recipients of spleen cells from immunized mice.