The aging immune system is characterized by the contraction of T cell receptor (TCR) diversity and the de novo expression of NKrelated receptors (NKR) on oligoclonal T cells. NKR+ T cells likely represent a secondary immune diversification as a biological adaptation of aging to ensure host defense despite shrinkage of the TCR repertoire. NKRs are expressed in various combinations even among TCR-identical cells, and are capable of triggering effector pathways in either TCR-independent or TCR-dependent fashion. Understanding the biology of NKR+ T cells will be pivotal to the development of strategies to enhance immunity in the elderly.