Natural killer cells in healthy aging

Immunosenescence is a process that affects all cell compartments of the imm une system. Age-associated changes have been demonstrated not only on T lym phocytes but also in different aspects of the innate immunity including nat ural killer (NK) cells. A significant expansion in the percentage of NK cel ls showing a mature phenotype has been found in healthy elderly donors, and the NK-cytotoxic capacity of total peripheral blood lymphocytes is well pr eserved in these individuals. However, NK-cell killing of K562 is impaired when considered on a per-cell basis. Furthermore, NK cells from elderly peo ple show a decreased proliferative response to interleukin 2 and a parallel impaired expression of the CD69 activation antigen. The response to interl eukin 2 of NK cells from aged donors is also impaired in terms of their cap acity to kill NK-resistant cell lines, but not when K562 killing, perforin synthesis, or tumor necrosis factor alpha production are considered. Theref ore phenotypic and functional alterations can be shown in NK cells in healt hy aging. These changes are compatible with the expansion of a mature NK su bset. (C) 1999 Elsevier Science Inc. All rights reserved.