CD4 and neoplasm: Oral administration of an attenuated S. Typhimurium strain harboring a eukaryotic expression plasmid encoding siRNA-Stat3 enhanced NK cell activity and T-lymphocyte function and elevated the percentage of CD8+ T cells, whereas it decreased the number of CD4+ CD25+ regulatory T cells in the tumor; these effects led to inhibition of tumor growth and prolonged survival of tumor-bearing mice122.