While the MHC class I-restricted antigen presentation to CD8+ T cells is thought to primarily mediate the anti-tumor immune response, and indeed there is substantial evidence that ablation induces cytotoxic T lymphocytes (reviewed in detail in subsequent sections), there is a growing appreciation for the role of CD4+ T cell-mediated anti-tumor immunity [31,32,33]. This evidence concerns the gene CD4 and neoplasm.