Natural Killer Cells, Aging, and Vaccination.

Aging is associated with changes in the immune system. Both (innate and adaptive) arms of the immune system are involved. Natural killer (NK) cells are part of the innate immune system. They participate in host defense by eliminating cells that are virally infected, transformed, or senescent. They are also able to modulate the adaptive part of the immune system. As all cells, NK cells are subjected to changes with aging, which affects both their phenotype and functions. Aging is associated with various latent chronic viral infections, and the most significant among them is CMV. It is difficult to distinguish between the influence of CMV infection and that of aging itself on the NK cell properties. Recently, NK cells have been shown to be an important player in vaccine efficacy, which is also decreased with aging. In this chapter, we describe age-related changes in NK cells and their possible influence on the efficacy of vaccination in old age.