CD8A and infection: The most well characterized age‐related alterations in the human immune system are in the T‐cell compartment, in particular CD8+ T cells, which show reduced numbers in age, commensurate with reduced naïve CD8+ T‐cell priming, limiting the ability of CD8+ T‐cell responses to be generated toward new infections (Briceno et al., 2016; Figure 1b).