Induction of a robust CTL response requires, CTL interaction with professional antigen-presenting cells, such as dendritic cells, displaying onco-antigenic peptide, often derived from tumor-associated antigens (TAAs) or neoantigens, and costimulation via CD4<sup>+</sup> T helper cells which then elicits an effector and memory immune response that targets and kills cancer cells. Here, CD4 is linked to cancer.