A Pro-Inflammatory Role of C5L2 in C5a-Primed Neutrophils for ANCA-Induced Activation

Background: The complement system is crucial for the development of antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV). In particular, C5a and its receptor on neutrophils, CD88, play a central role. The functional role of the second receptor of C5a, C5L2, remains unclear. In the current study, we investigated the role of C5L2 in C5a-primed neutrophils for ANCA-induced activation. Methods: The effect of blocking C5L2 by anti-human C5L2 blocking antibody were tested on respiratory burst and degranulation of C5a-primed neutrophils activated with ANCA, as well as on membrane-bound proteinase 3 (mPR3) and concentration of myeloperoxidase (MPO) in supernatant of C5a-primed neutrophils. An antagonist for CD88 was also employed. Results: Blocking C5L2 resulted in a significantly decreased MPO concentration in the supernatant of C5a-primed neutrophils. mPR3 expression increased from 209.0643.0 in untreated cells to 444.3660.8 after C5a treatment (P,0.001), and decreased to 375.8665.44, 342.2654.3 and 313.7643.6 by pre-incubating blocking C5L2 antibody at 2.5 mg/ml, 5 mg/m