CD4 and cancer: Although there has been a greater emphasis on CD8+ T cell responses in this context, perhaps due to the fact that they can directly recognize most tumors and the comparative ease in identifying the target NeoAgs presented by MHC-I versus MHC-II, the fact that CD4+ T cells are crucial for the priming and regulation of CD8+ T cells suggests that a deeper understanding of their response to cancer could significantly improve existing immunotherapies, including ACT.