Summary
This study was performed to determine whether, as an adjunct to cyclophosphamide (CY), a number of H-2-incompatible lymphoid cells too small to induce clinically evident graft-versus-host disease would exert a significant antitumor effect and whether clinically significant antitumor specificity might be imparted to a subclinical graft-versus-host reaction by preimmunization of the spleen cell donors. Adult BALB/c mice bearing a disseminated transplantable BALB/c Moloney virus-induced lymphoma (LSTRA) with tumor-associated antigens were treated with sublethal CY plus spleen cells from C57BL/6 mice that either were nonimmune or had been immunized with normal BALB/c tissue, a BALB/c chemical sarcoma, an antigenically related murine sarcoma virus (Moloney), or LSTRA cells. The results, represented by long-term survivors, showed that, in the absence of detectable graft-versus-host disease and in conjunction with CY, nonimmune spleen cells exerted a significantly greater antitumor effect than was observed with CY alone; that spleen cells immune to host isoantigens were no more effective than nonimmune cells; but that preimmunization of the spleen cell donors with murine sarcoma virus (Moloney), or LSTRA rendered their cells significantly more immunotherapeutically effective in the CY-treated tumor-bearing hosts.
Supported by Grant CA 10777 from the National Cancer Institute, NIH, USPHS.