Neutrophil degranulation in antineutrophil cytoplasmic antibody-negative pauci-immune crescentic glomerulonephritis

Background: Patients with pauci-immune crescentic glomerulonephritis (CrGN) are frequently found to have antineutrophil cytoplasmic antibodies (ANCAs). It has been demonstrated that ANCAs can induce neutrophil activation and degranulation, which plays an important role in the pathogenesis of ANCA-associated vasculitis. However, the pathogenesis of ANCA-negative pauci-immune CrGN is not clear. This study aims to investigate the evidence for neutrophil activation and degranulation at disease presentation in patients with renal biopsy-proven ANCA-negative pauci-immune CrGN. Methods: Sera from 20 patients with ANCA-negative pauci-immune CrGN and 22 patients with ANCA-positive pauci-immune CrGN were collected at presentation. Serum neutrophil gelatinase-associated lipocalin (NGAL) and lactoferrin (LF) were measured using commercial ELISA kits. Results: Serum levels of NGAL in ANCA-negative patients were significantly higher than those of ANCA-positive patients (940.8 +/- 676.5 ng/mL vs. 569.3 +/- 287.2 ng/mL, p<0.05). This was still the case after adjustment for renal function. Serum levels of LF in ANCA-negative patients were also significantly higher than those of ANCA-positive patients (24.92 +/- 6.13 U/mL vs. 18.48 +/- 6.89 U/mL, p<0.05). Conclusion: Neutrophil activation and degranulation occurs in patients with ANCA-negative pauci-immune CrGN in the absence of ANCA, and might be even more prominent than in their ANCA-positive counterparts.