Neutrophils Function and Identification of Prognostic Factors in Granulomatosis With Polyangiitis (Formerly Named Wegener's Granulomatosis).

Anti-neutrophil cytoplasm antibodies (ANCA)-associated vasculitis are rare diseases characterized by inflammation of blood vessels. Among the numerous cell types that play a role in vasculitis, one of the key actors is the neutrophil. Neutrophils are equipped with very powerful molecules that they use to destroy the invading microbes. Therefore, the mechanisms controlling neutrophil activation should be tightly controlled. If that is not the case, neutrophils may destroy the tissues of the host. This is what happens during chronic inflammation in vasculitis. Autoantibodies directed against neutrophils, ANCA, produced thus demonstrating that neutrophils are also targets of the immune system in these diseases. In addition, molecular studies provided evidence that genes normally silenced in mature neutrophils under normal conditions can be re-expressed in neutrophils from patients with ANCA-associated vasculitis thus strongly suggesting a profound deregulation of neutrophil functions in these conditions. Notably, the investigators have preliminary data showing that neutrophils from patients with granulomatosis with polyangiitis (GPA, formerly Wegener's granulomatosis), an ANCA-associated vasculitis, interfere with the normal phase of resolution of inflammation.

The objective of the investigators' study is to understand the mechanisms underlying this increased activation state and determine if neutrophils could be used to define prognostic markers by clinicians to optimize patients' care. Therefore, the investigators plan to study the expression of proteins implicated in GPA pathophysiology at the membrane of neutrophils when they undergo apoptosis. The investigators will also study the deregulation of protein expression in neutrophils. This point will be the molecular translation of neutrophil deregulation. This technique is powerful and well adapted to identify by mass spectrometry the proteins that will be differentially expressed between the control and the disease state. After identification of proteins differentially expressed in patients with GPA, the investigators will further investigate whether their expression is modulated during the disease course and/or modified by the treatment.

The investigators believe that understanding these neutrophil perturbations can lead to better monitoring of disease activity. Ultimately, the investigators may propose more targeted anti-inflammatory therapies which would be better tolerated by patients. the investigators also can identify new markers for disease activity which allow clinicians to define a better therapeutic strategy.