Exacerbated neutrophilia in the airways and matching blood in patients with severe COVID-19. (A) Representative gating strategy for all samples (supplemental Figure 1 for full gating strategy). (B) Representative plots demonstrating the inflammatory profile of pulmonary neutrophils, including NE, CD184 (CXCR4), and intracellular staining of IL-6, IL-8, and IL-1β, including the full stain and FMO controls. (C) Representative histograms showing the median fluorescence intensity (MFI) of key markers in healthy blood (blue), severe blood (gray), and severe ETA (green) samples. (D) MFI of CD16 (FCγRIII), NE, and CD63 (LAMP-3) reveal a GRIM-like phenotype in neutrophils from paired blood (gray circles) and lung (green squares) samples.