Increased Neutrophil CD64 and HLA-DR Expression in Severe COVID-19: A Case-Control Flow Cytometry Study.

Introduction:COVID-19 presents with various symptoms, including fever, dyspnea, and respiratory failure. Understanding its pathogenesis is crucial, particularly the role of early immune responders such as neutrophils.Objectives:The study aimed to investigate neutrophil phenotypes and activation in patients with severe COVID-19, focusing on the expression of key activation markers and their potential role in disease severity.Methods:A case-control study was conducted in Makkah City involving 88 participants. The study group consisted of 48 PCR-confirmed severe COVID-19 patients with elevated C-reactive protein (CRP) levels and proinflammatory cytokine levels, and the control group included 40 healthy individuals. EDTA-anticoagulated whole blood samples were collected from all participants. Neutrophil counts were obtained, and flow cytometry was performed to assess the expression of activation markers CD64 and HLA-DR on neutrophils.Results:Severe COVID-19 patients exhibited significantly elevated neutrophil counts compared to healthy controls. Flow cytometric analysis revealed significantly increased CD64 and HLA-DR mean fluorescence intensity on neutrophils from patients with severe COVID-19 compared with healthy controls, indicating a heightened state of neutrophil activation.Conclusion:Severe COVID-19 was associated with increased neutrophil activation, reflected by elevated CD64 and HLA-DR expression. These findings support the potential value of neutrophil immunophenotyping in characterizing innate immune dysregulation during severe COVID-19.