[Effects of TCGF (T-cell growth factor) on experimental malignant glioma-specific killer T-cell]

The immunoregulatory effects of TCGF (T-cell growth factor) on the generation and growth of syngeneic murine malignant glioma (20-methylcholanthrene-induced 203-glioma)-specific killer T-cell were investigated in C57BL/6 adult mice in order to clarify the immunopotential usefulness for anti-tumor local adoptive immunotherapy against malignant brain tumor. TCGF was prepared and assayed. Briefly, 5 x 10(6) ml mouse spleen cells were cultured with 2 microgram/ml concanavalin A in RPMI-1640 medium supplemented with 2% fetal calf serum for 24 hours. Culture supernatants were concentrated by ammonium sulphate precipitation (55 to 80% saturation) and purified by gel filtration (Sephadex G-100, a molecular weight from 30 to 36,000 daltons) and ion exchange chromatography (DEAE-cellulose, elution with 0.15 M in NaCl at ph 7.4). The purified TCGF had no IFN activity. Assays for TCGF was performed for quantitative analysis using 203-glioma-specific killer T cell clone (G-CTLL), which was obtained by limiting dilution method (0.3 cells/well in 96 well microtiter plate) and maintained for over 6 months in the presence of TCGF. Titer (U/ml) of TCGF was defined as the quantity of TCGF required to obtain one-half of the maximal stimulation of G-CTLL proliferation assay. It was confirmed that the specific killer T-cell against 203-glioma was generated in mice after intracranial as well as subcutaneous inoculation of the tumor cells. The killer T-cell activity of spleen cells, however, began to be severely impaired 2 weeks after intracranial inoculation concurrently with the increased intracranial pressure due to developing the tumor growth. Sensitized lymphocytes obtained from intracranial and subcutaneous tumor-bearing mice were assessed for CTL (cytotoxic T-lymphocyte) activity in MLTC (mixed lymphocyte-tumor cell culture) for 18 hours by microcytotoxicity assay. The specific cytotoxicity against 203-glioma cells was enhanced when sensitized lymphocytes from intracranial and subcutaneous tumor-bearing mice were pre-cultured with optimal TCGF (20 U/ml) for over 5 days. After the treatment of sensitized lymphocytes with anti-Thy-1 monoclonal antibody and complement, however, the specific cytotoxicity of sensitized lymphocytes was eliminated almost completely. Therefore, it was thought that TCGF possesses immunoregulatory effects of enhancement of killer T-cell activity. On the contrary, TCGF had no influence on normal T lymphocytes and the growth of 203-glioma cells in vitro.(ABSTRACT TRUNCATED AT 400 WORDS)