CD8A and infection: Advances in the last decade on the processes involved in immunosenescence support the idea that some of the accepted hallmarks of T-cell immunosenescence in humans, such as the decreased numbers of peripheral naïve T-cells and the accumulations of memory T-cells (especially affecting the CD8+ T-cell compartment), are determined not only by the lower output of T-cells due to thymus involution but also by the individual’s history of pathogen exposure, particularly to infection with CMV.