syngeneic fibroblasts transduced to secrete GM-CSF will enhance T-cell tumor reactivity. However, at increasing ratios of fibroblast: tumor cells in the vaccine, allogeneic fibrobiasts resulted in dimin

easily be cultured. Clinical studies using cytokine-secreting fibro blasts are also being conducted in cancer patients (9, 10). In this report, we have evaluated the relative efficacy of using allogeneic versus syngeneic fibroblasts transduced to secrete cyto hines as an adjuvant to tumor vaccination. We have reported previ ously in animal models that tumor cells transduced to secrete GM CSF5 will enhance reactivity to wild-type tumor cells of T cells derived from TDLNs (11, 12). This phenomenon is apparent in both weakly immunogenic (13) and poorly immunogenic murine tumor systems (1 i, 13). We found that the use of either allogeneic or syngeneic fibroblasts transduced to secrete GM-CSF will enhance T-cell tumor reactivity. However, at increasing ratios of fibroblast: tumor cells in the vaccine, allogeneic fibrobiasts resulted in dimin ished adjuvant activity. Our studies further characterized the potential mechanisms associated with this phenomenon. The use of ailogeneic cytokine-secreting fibroblasts is less effective than that of syngeneic fibroblasts in the application of tumor vaccines for active, specific immunotherapy.