Elevated IL-10 level exerts tumor-promoting effects by stimulating tumor cell growth and proliferation via STAT3 activation, by inhibiting apoptosis and by allowing immune surveillance escape through inhibition of DC function, downregulation of human leukocyte antigen (HLA) class I molecules on tumor cell surface, recruitment of Treg, suppression of NK cells cytotoxic activity and impaired activation of Th1 CD4+ and cytotoxic T cells (167–172). The gene discussed is CD4; the disease is neoplasm.