Immunotherapy of pulmonary metastases using monoclonal antibody to T-cell suppressor factor and interleukin 2

Tumor-induced immune suppression of the host may pose a barrier to successful immunotherapy. A monoclonal antibody (MAb 14-12) able to bind and inhibit murine soluble T-cell suppressor factor was tested for in vivo antitumor activity by treatment of mice bearing three-day established pulmonary metastases of a weakly immunogenic methylcholanthrene-induced fibrosarcoma (MCA 106). Administration intraperitoneally in combination with interleukin 2 (IL-2), a growth factor for activated T lymphocytes, resulted in a significant reduction (60% to 90%) of metastases. Neither IL-2 nor monoclonal antibody alone had significant antitumor effects. This study demonstrates in vivo potentiation of IL-2 antitumor activity with an anti-T-cell suppressor factor and points to possible strategies for clinical application.