CD4 and neoplasm: On the other hand, although CTLs can recognize and kill tumor cells to maintain the equilibrium of internal environment, playing a significant role in the tumor immunosurveillance, the CD4+ CD25+ Foxp3+ regulatory Tregs induced by various mechanism, enable to counteract the antitumor CTL response, resulting in the poor immunogens and immunosurveillance escape of tumor cells (Sakaguchi, 2005; Vignali et al., 2008).