CD4 and neoplasm: Other than the inhibition of cytotoxic functions of innate immunity as described above, TGF-β can also antagonize the adaptive immunity; and increasing evidence suggests that TGF-β signaling suppresses anti-tumor immunity by blocking the differentiation and functions of T helper1 (TH1), T helper 2 (TH2) CD4+ T cells and cytotoxic CD8+ T cells, while promoting the differentiation, function and survival of CD4+CD25+ forkhead box P3 (FoxP3) regulatory T cells (Tregs) cells (Nakamura et al., 2001; Thomas and Massagué, 2005; Tone et al., 2008).