Thus, CIITA-driven MHC-II positive tumor cells can perform not only antigen processing and presenting function in vitro at least for primed T cells of either human (29) or mouse (32) but, more importantly, they can prime in vivo naïve CD4+ TH cells and thus serve as bona fide APC to generate a strong adaptive immune response capable to protect against the tumor (43, 46). This evidence concerns the gene CD4 and neoplasm.