Enhancement of 3LL tumor growth by autosensitized T lymphocytes independent of the host lymphatic system

The present studies were performed in order to further investigate the paradoxical behavior of autosensitized lymphocytes which mediate 3LL tumor cytotoxicity when tested in vitro and promote tumor growth when tested in vivo. Using animals immunologically impaired by means of adult thymectomy and total‐body irradiation, it was observed that the tumor‐enhancing effect of autosensitized lymphocytes did not require the collaboration of host lymphocytes. Whereas bone‐marrow‐derived cells were devoid of activity, thymus‐derived cells were found to be the mediators of both in vitro cytotoxicity and in vivo tumor enhancement. These findings indicate that tumor enhancement mediated by in vitro autosensitized spleen cells was the result of a direct and specific interaction between committed T cells and self‐antigenic determinants carried by the tumor cells.