Flow Cytometric Analysis of Systemic and Airway Neutrophil Maturation and Activation in Lung Transplant Patients

Purpose The neutrophil is the most abundant blood leukocyte in humans and the first cell involved in an immune response like infection, rejection or injury of the lung. Neutrophils were long considered as simple short-lived cells. However, several distinct neutrophil subsets, maturation and activation stages with functional heterogeneity are identified. This spiked our interest to perform an in-depth neutrophil characterization, focusing on their maturation and activation characteristics, in broncho-alveolar lavage fluid (BALF) and peripheral blood of lung transplantation (LTx) patients who received standard immunosuppression. Methods BALF and blood neutrophils were microscopically evaluated and identified by multicolor flow cytometry (CD16+/CD66b+) to examine expression of maturation/activation markers and adhesion molecules (CD10, CD62L, CD11b, CD11c, CD15, HLA-DR) and chemoattractant receptors (CXCR1-4, CCR1-3, FPR1-2, C5aR and BLTR1) within healthy control subjects (n = 11), stable LTx patients (n = 8-14), and LTx patients with infection (n = 9) or chronic lung allograft dysfunction (n = 2-6). Results LTx patients had a significantly higher (p Conclusion We demonstrated a compromised maturation of neutrophils in peripheral blood and BALF of LTx patients versus healthy controls. In addition, we observed a more activated status of BALF neutrophils with a surprisingly increased expression of CXCR3 on their membrane in stable LTx patients.