The B <sub> 7 </ Sub> Genetically Modified Rat C6 Glioma Cells In Vitro Spleen Lymphocyte Activation And Tumorigenicity In Mice Experiments

T cell-mediated immunity response has been proposed to play a key role in the body's antitumor imunity. And the activation and proliferation of T cells are critical in this process. Tumor cells may escape immune surveillance due to lack of costimulatory singal which is essential for the activation of host immune system. Effective activation of T lymphocytes requires two signals from antigen presenting cells (APCs). The first signal is delivered upon the binding of TCR to MHC-foreign antigen complexes on APCs and the second signal is provided by the interaction of costimulatory molecules on T cells with their ligands on APCs. Many expriments indicated that the body's antitumor ability is enhanced when B₇ gene, a costimulatory singal gene is transduced into tumor cells.PURPOSE: To study the roles of tranduction of foreign B₇ gene into rat C6 glioma cells in inducing T cells activation and proliferation in vitro , and to investigate whether transduced B₇ gene in the C6 glioma cells can lead to alteration of tumorgenicity in vivo (subcutaneous, intracranial).METHODS: In preliminary experiments, a retroviral vector system PLXSN-B₇ including B₇ cDNA was constructed. The construct was introduced into C6 cells with the method of liposome. Transduced cells were selected in medium containing puromycin(500-700ug/ml). The roles of B₇ gene in the ex vivo activation and proliferation of T cells were investiged using the method of mixed cultures of T lymphocytes with C6 cells modified by B₇ (B₇-C6 group) or by vacant vector (V-C6 group). To study the change of tumorgenicity, B₇-C6 cells, V-C6 cells and C6 cells were inoculated (subcutaneous, intracranial) into Wistar rats.RESULTS: Cells modified by B₇ (B₇-C6) or vacant vector (V-C6) and cells unmodified (C6) were analyzed for cell-surface expression of B₇ by RNA-slot hibridization and immunofluorescence microscopy. The analysis indicated that the B₇-C6 cells were positive for expresion of B₇ while V-C6 cells and the parental C6 cells were negative. To examine whether the expression of B₇ cells might enhance the proliferation of T cells, splenocytes from Wistar rat bearing tumor were stimulated in vitro...