Sputum Antineutrophil Cytoplasmic Antibodies in Serum Antineutrophil Cytoplasmic Antibody-Negative Eosinophilic Granulomatosis with Polyangiitis.

RATIONALE: Eosinophilic granulomatosis with polyangiitis (eGPA) is a small-vessel vasculitis where 40% of patients present with serum antineutrophil cytoplasmic antibodies (ANCAs). We examined the presence and clinical relevance of sputum ANCAs in the serum ANCA- patients with eGPA. METHODS: ANCA was investigated in matched sputum and blood samples collected from 23 patients with eGPA (n = 10, serum ANCA+), 19 patients with eosinophilic asthma (prednisone dependent), and 13 healthy volunteers. IgG reactivity to common target antigens and cytokine profiles in sputum samples were examined. Pathogenicity of detected sputum ANCA was assessed using in vitro degranulation assays. MEASUREMENTS AND MAIN RESULTS: Most patients with eGPA (17 of 23, 74%) showed significantly increased sputum ANCAs compared with patients with eosinophilic asthma (P = 0.002) and healthy controls (P < 0.0001), irrespective of their serum ANCA status. In addition, 16 of 17 (94%) of sputum ANCA+ patients had clinical manifestations of severe asthma compared with 3 of 6 (50%) in the sputum ANCA- subset (P = 0.04). Microarray analysis of 123 common antigens failed to reveal a specific target for the ANCA IgG. However, immunoprecipitated immunoglobulins from ANCA+ sputum allowed extensive extracellular trap formations from both neutrophils and eosinophils in vitro, indicating pathogenicity of detected IgG autoantibodies. Cytokine analysis showed lung-localized increases in CXCL8 (neutrophil/eosinophil chemotaxis), CCL24 (eosinophil recruitment), and CXCL12 (lymphocyte recruitment) in the sputa from ANCA+ patients (P < 0.01). CONCLUSIONS: We report a novel finding of ANCA reactivity in the sputa of patients with eGPA in whom disease severity is driven by respiratory complications. Investigating localized autoimmunity may lead to the discovery of novel pathomechanisms, therapeutic targets, and optimal biomarkers for diagnosing and managing eGPA.

Sputum autoantibodies in patients with severe eosinophilic asthma.

BACKGROUND: The persistence of eosinophils in sputum despite high doses of corticosteroids indicates disease severity in asthmatic patients. Chronic inflamed airways can lose tolerance over time to immunogenic entities released on frequent eosinophil degranulation, which further contributes to disease severity and necessitates an increase in maintenance corticosteroids. OBJECTIVES: We sought to investigate the possibility of a polyclonal autoimmune event in the airways of asthmatic patients and to identify associated clinical and molecular characteristics. METHODS: The presence of autoantibodies against eosinophil peroxidase (EPX) and anti-nuclear antibodies was investigated in patients with eosinophilic asthma maintained on high-dose corticosteroids, prednisone, or both. The ability of sputum immunoglobulins to induce eosinophil degranulation in vitro was assessed. In addition, the associated inflammatory microenvironment in patients with detectable autoantibodies was examined. RESULTS: We report a "polyclonal" autoimmune event occurring in the airways of prednisone-dependent asthmatic patients with increased eosinophil activity, recurrent pulmonary infections, or both, as evident by the concomitant presence of sputum anti-EPX and anti-nuclear antibodies of the IgG subtype. Extensive cytokine profiling of sputum revealed a TH2-dominated microenvironment (eotaxin-2, IL-5, IL-18, and IL-13) and increased signalling molecules that support the formation of ectopic lymphoid structures (B-cell activating factor and B cell-attracting chemokine 1). Immunoprecipitated sputum immunoglobulins from patients with increased autoantibody levels triggered eosinophil degranulation in vitro, with release of extensive histone-rich extracellular traps, an event unsuppressed by dexamethasone and possibly contributing to the steroid-unresponsive nature of these eosinophilic patients. CONCLUSION: This study identifies an autoimmune endotype of severe asthma that can be identified by the presence of sputum autoantibodies against EPX and autologous cellular components.