Sizes of Immune Cell Subsets Correlate with Human Mortality

In this study, we found that T cells and natural killer (NK) cells with low expression of CD56 were inversely associated with mortality while neutrophils were positively associated with mortality. In addition, we found myeloid dendritic cells to be nominally associated with a reduced odds of mortality, and CD4+ effector memory T cells and IgD- memory B cells to be nominally associated with increased mortality odds. Several previous studies have shown a positive association between neutrophils and mortality and our study confirmed these previous findings. The number of neutrophils are preserved in older adults though their phagocytic ability is impaired. Furthermore, since neutrophils are pro-inflammatory, higher numbers of neutrophils in older adults may increase the odds of mortality. NK cells cytotoxicity and IFN-γ production decreases in old age, and low cytotoxicity is associated with increased morbidity and mortality. NK LO cells have significantly higher cytotoxicity than NK Hi cells. Hence, the observed inverse association with mortality was consistent with the biological activity of this NK cell subtype. A higher percentage of myeloid subset of dendritic cells was associated with reduced mortality, which was consistent with previous studies showing that dendritic cells mediate antitumor immune responses, and were used in immunotherapies and vaccinations that resulted in improved survival of cancer patients. The absolute count of T cells decreases with a...
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