TH1 TYPE CD4(-CELLS MAY BE A POTENT EFFECTOR AGAINST POORLY IMMUNOGENIC SYNGENEIC TUMORS - ANTITUMOR-ACTIVITY OF TH1 TYPE CD4(+) T-CELLS() T)

We examined the possibility that Th1 type CD4(+) T cells may be an eff ector against three kinds of syngeneic tumors such as highly immunogen ic B16 melanoma (B16) and two poorly immunogenic lines of MCA fibrosar coma (MCA) and 3LL carcinoma (3LL). In a proliferation assay, the Th1 type CD4(+) T cell clone (MH2) recognized the purified protein derivat ives (PPD) derived from Mycobacterium tuberculosis. In a tumor-neutral izing assay, MH2 showed anti-tumor activity against both B16 and MCA. In a model of pulmonary metastasis, MH2 also showed anti-tumor activit y against both B16 and 3LL. In an assay of cytolysis, MH2 showed a mod erate level of tumor necrosis factor-dependent cytolytic activity only against MCA. In a cytostasis assay, MH2 showed a high level of interf eron gamma-dependent cytostatic activity against the three tumors in t he presence of macrophages. The anti-tumor activity of MH2 against B16 and 3LL was suggested to be, at least in part, attributable to the au gmented natural killer activity. Taken together, these findings sugges t that we may potentially be able to utilize Th1 type CD4(+) T cells a s an effector for immunotherapy against poorly immunogenic tumors.