Sustained CD8+ effector T-cell responses, the aim of each cancer vaccine, require CD4+ T-cell help [45, 46], ideally from the same epitope, which can only be achieved when the antigen (synthetic long peptides or proteins) is processed intracellularly by DCs and the resulting peptide fragments are presented on both MHC class I and II molecules [47]. This evidence concerns the gene CD4 and cancer.