WITHDRAWN: Age-related changes of neutrophil characteristics, potential of activation, DNA release and NET formation

Abstract

Background: Neutrophils are a heterogeneous population of leukocytes, which can be subdivided into high and low density neutrophils (HDNs/LDNs). They are known to fight intruders with different mechanisms, including the release of neutrophil extracellular traps (NETs), which have also been associated with thrombosis. Risk of both, thrombosis and infections, increase with age. Differences in neutrophil subpopulations and functionality have been shown in various disease states, but investigations in healthy subjects and their dependence on age are lacking. The aim of this study was to investigate age-related changes in neutrophils regarding neutrophil subpopulations, their potential of activation, DNA release and NET formation. Methods: Neutrophil subpopulations (HDNs and LDNs) were isolated from 25 healthy individuals subdivided into 3 groups (<45 years, n=8; 45-54, n=9; >54, n=8). Neutrophil characteristics, potential of activation and the ability of NET formation were investigated using flow cytometry. Externalisation of DNA was detected by a DNA release assay. Results: HDN and LDN counts did not differ between age-groups. However, with increasing age we observed a shift in neutrophil subpopulations towards a lower amount of mature LDNs, characterized by their expression of membrane receptors CD62L and CD16. Upon stimulation, neutrophils of older individuals showed significantly higher release of DNA. NET formation was associated with increasing age. HDNs of younger participants increased activation markers (CD66b and CD11b) to a higher extent compared to those of older individuals. Conclusion: Neutrophils and their ability of activation, DNA release and NET formation change with age and this might contribute to the higher risk of infection and thrombosis at advanced age. Furthermore, these results highlight the importance and necessity of age-matching in studies that focus on neutrophil characteristics.