Functional alteration of granulocytes, NK cells, and natural killer T cells in centenarians

The immune system in centenarians was characterized as elevated levels in t he proportion and number of granulocytes, NK cells, and extrathymic T cells (including NKT cells) in the peripheral blood. Conventional T cells, abund ant in youth, were decreased in proportion and number. In addition to this numerical change in centenarians, the function was significantly altered in comparison with that in middle-aged subjects. The phagocytic function and cytokine production of granulocytes in centenarians increased whereas the p roduction of superoxides from granulocytes decreased. This tendency was alm ost the same in both healthy and unhealthy centenarians. IFN gamma producti on by NK and extrathymic T cells in centenarians seemed to be augmented and resulted in an elevated level of serum IFN gamma. Possibly due to the effe ct of this endogenous IFN gamma, the proportion of CD64(+) (Fc gamma RI) ce lls among granulocytes was elevated. The expansion of CD64 antigens on gran ulocytes is known to be regulated by IFN gamma and to be associated with th eir induction of phagocytosis. These results suggest chat the immune system of centenarians is not merely impaired, but altered in terms of the number and functions of granulocytes, NK cells, NKT cells. Human Immunology 61, 9 08-916 (2000). (C) American Society for Histocompatibility and Immunogeneti cs, 2000. Published by Elsevier Science Inc.