Tumor-specific immunity induced by somatic hybrids. II. Elicitation of enhanced immunity against the parent plasmacytoma.

Hybrid cells derived from fusion of a BALB/c plasmacytoma (TEPC-15) and L cells (C3H origin) were used to stimulate tumor-specific immunity against the parental plasmacytoma cells. Live hybrid cells induced tumor-specific immunity against TEPC-15 more effectively than mitomycin-treated hybrid or TEPC-15 tumor cells. Adoptive transfer of immunity with spleen cells of mice immunized with hybrid cells was also more effective than that with mitomycin-treated tumor cells. The immunity induced by the hybrid cells was specific to the TEPC-15 tumor because the mice that received immune spleen cells were not protected against challenge with either HOPC-8 or McPC-603 plasmacytomas. T cell populations were primarily responsible for the transfer of specific immunity based on the sensitivity of immune cells to anti-Thy 1.2 and complement. Mice that had established solid tumors were treated with 5 x 10(7) spleen cells to evaluate the therapeutic value of the hybrid-induced immune cells. Tumors in the mice that received immune cells gradually regressed over a 40-day period, whereas tumors on the control mice continued to grow. These results suggest that a rearrangement of tumor-specific antigens on allogeneic hybrid cells can enhance their immunogenicity.