CHANGES IN NATURAL-KILLER-CELLS, THE CD57CD8 SUBSET, AND RELATED CYTOKINES IN HEALTHY AGING

Aging has been shown to be accompanied by various changes in the lymph ocyte subset distribution in the elderly. We have investigated more fu lly, and in a large number of subjects, age-related changes within sev eral subpopulations bearing natural killer (NK) cell-associated surfac e antigens and changes in several cytokines involved in NK cell expans ion. A total of 229 healthy subjects from all decades of life from 20 to 98 years of age was included in this cross-sectional study. A signi ficant increase with age was found in both the absolute counts and the proportions of CD3-CD(16+56)+, CD3+CD(16+56)+, CD57+CD8+, CD57+CD8((l ow))+, and CD57+CD8- cells, whereas the CD57+CD8((high))+ subset, whic h may represent the cytolytic T cell population more precisely, showed less change with age. Some evidence is also provided to suggest that these expanded NK cell populations are in an activated state. Soluble IL-2 receptor levels were also found to increase significantly with ag e and correlated with certain NK cell subsets. Although the functions of some of these subsets remain to be elucidated, their expansion in t he elderly may represent a remodeling of the immune system with increa sing age, with an increase in non-MHC-restricted cells perhaps compens ating for the previously reported decline in T and B cells in the elde rly. Alternatively, increased numbers of these cells may be a direct r esult of cytokine dysregulation or increased antigenic or neoplastic c ell challenge.