Immunosenescence is the steady degeneration of the immune system that occurs with age in humans and animals. Multiple aspects of the immune response are severely disregulated by aging, among which the T cell immune response is the most dramatically affected. T cell-mediated production of cytokines Interleukin (IL)-2 and Interferon (IFN)-γ decreases significantly with age. 

 

The amount of IFN-γ decreases along with the activity of T Helper 1 (Th1) cells and the amount of IL-4 and IL-10 increases along with the activity of T Helper 2 (Th2) cells, resulting in a decreasing ratio of Th1/Th2 in elderly people. The decrease in the numbers of Natural Killer (NK) cells and Natural Killer T (NKT) cells contributes to the deleterious immune response in the elderly, and the number of myeloid Dendritic Cells (DCs) also progressively declines with age.