C-ANCA-positive IgG fraction from patients with Wegener's granulomatosis induces lung vasculitis in rats

Abstract

SUMMARYThe aim of the present study was to analyse in rats the ability of C-ANCA-positive IgG fraction in triggering inflammatory response on pulmonary tissue. Wistar rats (n = 18) were injected via the the internal jugular vein with 20 mg of total C-ANCA-positive IgG fraction isolated from serum of three different Wegener's granulomatosis patients obtained before therapy. Similarly, control rats were treated with IgG fraction from two rheumatoid arthritis patients (n = 7), IgG from six normal human sera (n = 15) or saline (n = 18), respectively. Animals were sacrificed after 24 h of injection for histological analysis of the lungs. Vasculitis and inflammatory infiltrate were consistently absent in rats injected with rheumatoid arthritis IgG or saline and in 14/15 of normal IgG treated animals. In contrast, marked vasculitis was observed in all 18 animals injected with C-ANCA-positive IgG fraction. The histological features were characterized by the presence of a perivascular pleomorphic cellular sheath, particularly around small vessels, endothelial adherence and diapedesis of polymorphonuclear leucocytes and presence of granuloma-like lesions. A dose-response relationship was observed between protein concentration of C-ANCA IgG sample and the intensity of the inflammatory response in the animals. In addition, IgG fraction with undetectable C-ANCA, obtained from one patient in remission after treatment, was not able to reproduce the pulmonary tissue alterations induced by its paired IgG that was positive for C-ANCA taken before therapy. The experimental model described herein may be useful to characterize more effectively the pathogenic mechanism of C-ANCA in Wegener's disease.

Anti-endothelial cell antibodies (AECA) in patients with propylthiouracil (PTU)-induced ANCA positive vasculitis are associated with disease activity

“…In the latter, the majority of ANCA recognized only a single target antigen such as MPO or PR3, while PTU-induced ANCA were polyclonal B cell activation, and multiple ANCA target antigens could be recognized by one serum and the target antigens included MPO, PR3, HLE, LF, bactericidal/permeability-increasing protein (BPI), cathepsin G (CG) and azurocidin (AZU) [2,7,8]. Increasing evidence has suggested that ANCA might play an important role in the pathogenesis of primary small vasculitis [9,[25][26][27][28][29][30][31][32][33][34][35][36][37]. However, our previous work demonstrated clearly that the majority of PTU-induced ANCA positive patients did not show clinical evidence of vasculitis [7,8].…”

Animal Models of ANCA Associated Vasculitis

“…Other systems have modeled PR3-AAV associated pulmonary involvement. C-ANCA from patients with GPA was transferred to Wistar rats (123). All animals displayed marked pulmonary vasculitis 24 h after antibody transfer in a dose-dependent manner [despite the limited homology between human and mouse PR3 (106)], with no disease observed in mice treated with control IgG.…”

Experimental Autoimmune Vasculitis

“…To accurately assess lung histology, it is necessary to intubate the trachea to ensure full lung inflation at the time of fixation. 21 We did not do this, so it was not possible to accurately quantify lung vasculitis, beyond general comments about the presence or absence of intra-alveolar hemorrhage and perivascular leukocyte cuffing. We did, however, find that the lungs of many treated rats displayed petechiae over their surface at the time of sacrifice.…”