α-1 Antitrypsin regulates human neutrophil chemotaxis induced by soluble immune complexes and IL-8
David A. Bergin, … , Shane J. O’Neill, Noel G. McElvaney
David A. Bergin, … , Shane J. O’Neill, Noel G. McElvaney
Published November 8, 2010
Citation Information: J Clin Invest. 2010;120(12):4236-4250. https://doi.org/10.1172/JCI41196.
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α-1 Antitrypsin regulates human neutrophil chemotaxis induced by soluble immune complexes and IL-8

Abstract

Hereditary deficiency of the protein α-1 antitrypsin (AAT) causes a chronic lung disease in humans that is characterized by excessive mobilization of neutrophils into the lung. However, the reason for the increased neutrophil burden has not been fully elucidated. In this study we have demonstrated using human neutrophils that serum AAT coordinates both CXCR1- and soluble immune complex (sIC) receptor–mediated chemotaxis by divergent pathways. We demonstrated that glycosylated AAT can bind to IL-8 (a ligand for CXCR1) and that AAT–IL-8 complex formation prevented IL-8 interaction with CXCR1. Second, AAT modulated neutrophil chemotaxis in response to sIC by controlling membrane expression of the glycosylphosphatidylinositol-anchored (GPI-anchored) Fc receptor FcγRIIIb. This process was mediated through inhibition of ADAM-17 enzymatic activity. Neutrophils isolated from clinically stable AAT-deficient patients were characterized by low membrane expression of FcγRIIIb and increased chemotaxis in response to IL-8 and sIC. Treatment of AAT-deficient individuals with AAT augmentation therapy resulted in increased AAT binding to IL-8, increased AAT binding to the neutrophil membrane, decreased FcγRIIIb release from the neutrophil membrane, and normalization of chemotaxis. These results provide new insight into the mechanism underlying the effect of AAT augmentation therapy in the pulmonary disease associated with AAT deficiency.

Authors

David A. Bergin, Emer P. Reeves, Paula Meleady, Michael Henry, Oliver J. McElvaney, Tomás P. Carroll, Claire Condron, Sanjay H. Chotirmall, Martin Clynes, Shane J. O’Neill, Noel G. McElvaney

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Figure 1

Chemotactic analysis of neutrophils in response to AAT.

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Chemotactic analysis of neutrophils in response to AAT. (A) Increased me...
(A) Increased mean chemotactic index of ZZ-AATD neutrophils (n = 6) compared with healthy control (MM) cells (n = 6) in response to IL-8 (10 ng/2 × 107 cells). Assays were preformed in PBS or serum (50% v/v) from respective ZZ or MM individuals. (B) Decreased mean chemotactic index of ZZ-AATD neutrophils (n = 6) in PBS in response to sIC (10% v/v), yet increased mean chemotactic index of ZZ-AATD neutrophils in serum (50% v/v) compared with healthy control cells (n = 6). (C) An increase in chemotactic inhibition efficiency of increasing concentration of AAT (0.2–27.5 μM). Black bar, positive IL-8 (10 ng) control; white bar, negative HSA (27.5 μM) control. *P < 0.05 versus IL-8 control. (D) Neutrophil chemotaxis in a linear gradient of IL-8 (1, 10, 20, or 40 ng) or complex gradient in the presence of inhibitory AAT (27.5, 6.9, 0.9, 0.2 μM) (*P < 0.05 compared with AAT-untreated cells). (E) Increased chemotactic inhibition efficiency of increasing concentrations of AAT (0.4–27.5 μM). Black bar, positive sIC (10% v/v) control; white bar, negative HSA (27.5 μM) control. *P < 0.05 versus sIC control. Experiments illustrated in A–E were performed in triplicate on 3 consecutive days, and for comparative analysis the PBS control was set at a chemotactic index of 1. Each measurement is the mean ± SEM.