Compared to healthy donors, the peripheral blood of breast cancer patients harbours functionally impaired mature T cell subsets with reduced secretion of pro-inflammatory cytokines (IL-2, IFN-γ), defective responsiveness to IL-6, reduced T cell receptor (TCR) signaling [27], and circulating CD8+ T cells display senescent (KLRG1+NKG2+) or exhausted (CD27−CD28−PD-1+) phenotypes [28]. This evidence concerns the gene CD8A and breast cancer.