The capacity of CD4+ T cells to differentiate into Th1 effector cells tends to decrease with age [35], thus it is tempting to speculate that a subsequent decrease in IFN-ɣ production in the microenvironment of the mammary gland lifts the inhibition on luminal differentiation enabling accumulation of these putative cancer cells-of-origin with age. Here, IFNA1 is linked to cancer.