Autologous erythrocytes inhibit neutrophil oxidative burst, chemotaxis, extracellular trap formation and apoptosis. (A) Purified human neutrophils were coincubated in whole-blood components: plasma, erythrocytes, or both plasma and erythrocytes. Coincubation was done with whole plasma, and the erythrocyte concentration was at a 1:50 neutrophil:erythrocyte ratio. MFI of phagosomal ROS production was analyzed using Fc-OxyBURST Green assay reagent after 15 minutes; n = 3 Statistics were analyzed by ordinary 1-way analysis of variance (ANOVA). ****P < .0001. (B) The effect of neutrophil chemotaxis in combination with erythrocytes (neutrophils:erythrocytes; upper well) in the presence of 100 nM of fMLP (lower well) was determined using a transwell system. Statistics were analyzed by ordinary 1-way ANOVA; n = 4. *P < .03 versus control values considered statistically significant. (C) NET formation was quantified to determine the effect of erythrocytes incubated with neutrophils; n = 3. Statistics were analyzed by ordinary 1-way ANOVA. ***P < .0001 versus control values considered statistically significant. (D) NET formation microscopy analysis with increasing concentrations of erythrocytes plus phorbol myristate acetate (25 nM) where indicated. Scale bar, 50 μm. (E) Detection of apoptotic neutrophils was analyzed by TUNEL assay with and without incubation with erythrocytes up to 8 hours. Neutrophils were gated using forward and side scatter by flow cytometry and by TUNEL MFI of 10 000 cell counts. Results were analyzed by Student paired t test; n = 2. *P < .05 versus control values considered statistically significant. N:E, neutrophil:erythrocyte; PMA, phorbol myristate acetate; RFU, relative fluorescence units.