Regulation of immune responses against the syngeneic ADJ-PC-5 plasmacytoma in BALB/c mice. I. Analysis of immune parameters involved.

The non-secreting variant of ADJ-PC-5 plasma cell tumour of BALB/c mice is a highly malignant tumor, the LD50 being 3 x 10(1) cells/mouse after intraperitoneal injection. Nevertheless, immunization against the tumour is possible. Four injections of 10(7) X-irradiated tumour cells at weekly intervals render up to 95% of mice resistant to an otherwise lethal challenge with 10(3) living tumour cells. The immune responses are both T cell-mediated cellular cytotoxicity and antibody-mediated cytotoxicity as assessed by in vitro tests. Immunity can also be transferred in vivo into recipient mice by either spleen cells or immune sera. Specificity of both types of immune responses was determined. The results indicate that the cell-mediated and the humoral immune response are directed against cell-surface antigens associated with endogenous murine leukemia virus.