CD10⁺NDNs from GDs inhibit proliferation and IFNγ production by T cells via CD18-mediated contact-dependent ARG1 release. (A-C,E) CD3/CD28-stimulated T cells were cultured for 96 hours in the absence or the presence of CD10⁺ NDNs from HDs or GDs, added at a 5:1 neutrophil-to-T-cell ratio, with or without: 10 µg mL⁻¹ anti-CD18 or isotype control mAbs (A-B), 200 µg mL⁻¹l-arginine (C), 250 U mL⁻¹ catalase (E). The percentages of increase and decrease of proliferation, as measured by BrdU incorporation (A,C,E) or IFNγ production (B) by T cells, are reported. Graph values indicate medians from independent experiments (n = 5-10). **P ≤ .01; ***P ≤ .001, by the Mann-Whitney U test. (D) The panel displays arginase activity, as evaluated by specific enzymatic assay, in supernatants from CD3/CD28-stimulated T cells cultured for 96 hours in the absence or the presence of CD10⁺ NDNs from HDs or GDs (with or without 10 µg mL⁻¹ anti-CD18 or isotype control mAbs) at a 5:1 neutrophil-to-T-cell ratio. Graph values indicate medians from independent experiments (n = 9). *P ≤ .05, by the Mann-Whitney U test.