Mem 166

Peripheral blood was collected in EDTA vial, and 200 μl of blood was aliquoted for antibody staining. Briefly, 1 ml of RBC lysis buffer was added to 200 μl of whole blood, and mixed properly. A 10× red blood cell lysis buffer was prepared in-house using NH₄Cl (0.155 M), KHCO₃ (0.01 M) and EDTA (0.1 mM). The tubes were incubated for 10 min at 4 °C, and centrifuged at 300×g for 10 min. The cell pellets were washed twice with 1× PBS and suspended in 300 μl of PBS to obtain a single cell suspension. For cell surface staining, 100 μl of cell suspension was used, and the antibodies CD16 (1:100) (clone 3G8, APC conjugated, Cat No 302011, Biolegend, USA), CD66b (1:100) (clone G10F5, FITC conjugated, Cat No 305103, Biolegend, USA) and CD177 (1.5:100) (clone MEM-166, APC/Cyanine 7 conjugated, Cat No 315809, Biolegend, USA) was used. Unstained controls, stained samples, and fluorescence minus one controls were acquired on BD-LSR Fortessa flow cytometry machine. Using the FACS DIVA software, PMN gating was done based on FSC-A v/s SSC-A plot. Enriched and activated neutrophils were gated based on CD16⁺ CD66b⁺ (double positive) in a quadrant plot. CD177⁺ neutrophils were gated within these double positive cells.