A well-defined ratio of CD4 + and CD8 + T cells, such as a 1:1 ratio, has been shown to enhance efficacy by combining the direct tumour-killing ability of CD8 + T cells with the cytokine support provided by CD4 + T cells, particularly Th1-skewed cells that secrete IFN-γ, IL-2, and TNF-α [200, 201]. This evidence concerns the gene CD8A and neoplasm.