CD4 and breast cancer: Recent findings from several clinical studies have shown that markers of T-cell senescence (i.e. the loss of CD28 and/or gain of CD57 among CD4+/CD8+ T-cell) (13, 14) and T-cell exhaustion (i.e. high expression of PD-1 among CD4+/CD8+ T-cell) (15) are usually higher in patients with HIV infection, breast cancer or myeloid leukemia (AML) than in healthy controls (16).