(A) Neutrophil population frequency comparison between GCA and HC (GCA, n = 14; HC, n = 16). Unpaired nonparametric Mann-Whitney U test was used for statistical analysis. Data are presented with median ± IQR. (B) Correlation of CD10^hi and CD10^lo LDNs at baseline and follow-up after a single high-dose prednisolone treatment. Spearman’s correlation coefficient was calculated (baseline, n = 13; follow-up, n = 13). (C) Correlation of neutrophil subset frequency at baseline and follow-up. CD10^loCD64⁺CD16^lo and total CD10^lo LDNs showed significant negative correlation. A nonparametric paired Wilcoxon test was used for statistical analysis to compare the difference of neutrophil populations between baseline and follow-up measurement within the same patients. (D) The apoptotic rate of immature CD10^loCD64^–CD16^hi and CD10^loCD64⁺CD16^lo LDNs was significantly reduced compared with mature CD10^hi NDNs and LDNs after 24 hours in vitro culture as evidenced by caspase-3 staining (no growth factor in presence). Quantification of caspase-3–activated cells was performed by counting FITC⁺ out of the total DAPI⁺ cells. Three independent experiments were performed on FACS purified neutrophil populations from 3 GCA patients. The quantification was carried out by counting cells from 4–5 fields of a total of 100–200 cells of each population of each donor. Data are presented as mean ± SD. Nonparametric 1-way ANOVA Kruskal-Wallis test was used for statistical analysis. (E) CD10^loCD64⁺CD16^lo LDNs could survive up to 5 days in vitro, even without the presence of neutrophil growth factors such as G-CSF and GM-CSF. (F) CD10^loCD64⁺CD16^lo LDNs retained the proliferation capacity up to 3 days in culture measured by Ki67 expression, which is associated with cellular proliferation. Histograms from 1 representative GCA donor are shown. Three independent experiments were performed on FACS purified neutrophil populations from 3 GCA patients in E and F. *P ≤ 0.05, **P ≤ 0.01, ***P ≤ 0.001, ****P ≤ 0.0001.