In vivo Antitumor Mechanism of Natural Human Tumor Necrosis Factor Involving a T Cell‐mediated Immunological Route

We have investigated the in vivo antitumor mechanism of natural human tumor necrosis factor (n‐TNF) isolated from a culture of human leukemic B cell line (BALL‐1), especially its action as an immunomodulator, and found that the in vivo antitumor effect of n‐TNF on Meth A sarcoma implanted in BALB/c mice pretreated with monoclonal antibody against T cell‐specific surface antigen (Thy‐1) was significantly diminished. Furthermore, when BALB/c mice were treated with T cell subset‐specific monoclonal antibodies, anti‐L3T4 or anti‐Lyt‐2.2, the antitumor effect of n‐TNF on Meth A sarcoma was significantly reduced. Therefore, it was suggested that the in vivo antitumor mechanism of n‐TNF might involve a T cell‐mediated immunological route.