CD4 and neoplasm: Since clonal expansion of tumor antigen specific T cells induced by Ad-Flt3L-TK was inhibited by PC61 administration, we next determined whether PC61 affects the influx of CD4+ and CD8a+ T cells into the tumor, the draining lymph nodes and the spleen after treatment with Ad-Flt3L and Ad-TK (Fig. 7 B).