We address the CD4 T-cell help, the antigen-specific CD8 T-cell response and involved DCs populations in different tissues using two different tumor-mouse models characterized by the oncoviral antigen E7 in the TC-1 model or three neo-antigens in the MC-38 model (Adpgk, Reps1 and Rpl18), where antigen competition can be further addressed in the latter. The gene discussed is CD4; the disease is neoplasm.