Tumor-specific immunity induced by somatic hybrids. III. Persistence of adoptively transferred immunity specific for TEPC-15 plasmacytoma in normal BALB/c mice

Immunity against TEPC-15 tumor cells was induced in BALB/c mice by injecting semi-allogeneic hybrid cells derived from fusion of TEPC-15 tumor cells with LM(TK^-) cells of the C3H origin. Adoptive transfer of spleen cells from the immune mice into normal BALB/ c recipients rendered them free from tumors following tumor challenge; the recipients were most significantly protected from the tumor when tumor cells were injected 7-14 days after the adoptive transfer of immune cells. Such immunity following adoptive transfer appeared to persist in the recipients for at least 60 days. Moreover, the tumor-specific immunity was consecutively transferable (more than nine passages) into normal BALB/c recipients by serially passing spleen cells from the recipients every 14 days, without further stimulation with the hybrid cells or inactivated TEPC-15 tumor cells. Such consecutive transfer of the immune spleen cells induced splenomegaly in the recipients: a two- to five-fold increase over normal spleen cell recipients. The ability of spleen cells to transfer immunity, but not splenomegaly, was abrogated by treatment with mitomycin C. These results suggest that proliferation of donor cells is necessary to transfer immunity, and that splenomegaly alone does not manifest such immunity in the recipients.