Although cytokine production, such as IL-2 and IFN- γ, is a classical model for the function of CD4+ T cells in tumor immunity, the CD40L–CD40 axis that activates DCs through CD4+ T cells and the CD70–CD27 axis that activates CTLs through activated DCs constitute a new concept for helper function (26, 43). Here, CD70 is linked to neoplasm.