Myeloid cell response to NLRP3 inflammasome stimulation in recovered COVID-19 patients. Peripheral blood cells of recovered COVID-19 patients were collected 30 to 50 days after the first analysis. Whole peripheral blood cells of recovered COVID-19 patients were analyzed by flow cytometry using CD45, CD16, and CD66b markers. (A) Whole peripheral blood was treated with vehicle (control) or nigericin (5 µM) for 30 minutes and CD66b⁺CD16^dim granulocytes were analyzed for FAM-FLICA MFI (caspase-1 activation). (B) Histogram of FAM-FLICA signal in CD66b⁺CD16^dim cells. Light colors, FAM-FLICA in the control condition; dark colors, FAM-FLICA in the nigericin-treated condition. The dotted line represents the gate used to determine the percentage of FAM-FLICA⁺ cells. (C) Whole peripheral blood was treated with vehicle (control) or nigericin (5 µM) for 30 minutes and CD14^dimCD16⁺ were analyzed for FAM-FLICA MFI (caspase-1 activation).