Neutrophil and endothelial cell activation in the vasa vasorum in vasculo-Behcet disease

Aim: The aim of this study was to analyse the immunopathological mechanisms of vasculo-Behcet disease, which were also compared to cases of Takayasu's arteritis and inflammatory aneurysm to evaluate differences in inflammatory mechanisms. Methods and results: We reviewed six cases of vasculo-Behcet disease, four of Takayasu's arteritis and seven inflammatory aneurysms which underwent surgical repair. Immunohistochemical studies were performed on paraffin-embedded tissue using a labelled streptavidin-biotin method, as was in-situ hybridization for Epstein-Barr virus. Microscopically, neutrophils and lymphocytes accumulated around the vasa vasorum. Neutrophils were prominent as compared to Takayasu's arteritis and inflammatory aneurysm. Elastic fibres were not severely destroyed. Endothelial cells (ECs) of most vasa vasorum expressed HLA-DR. The number of vasa vasorum around which inflammatory infiltrating cells were observed in vasculo-Behcet disease was significantly greater than in inflammatory aneurysms and Takayasu's arteritis (P < 0.001). The cytokines IL-1α, TNF-β and IFN-γ were expressed in neutrophils and lymphocytes which were distributed around vasa vasorum, as well as neutrophils adherent to HLA-DR positive ECs. Conclusion: Our results suggest that vasculo-Behcet disease should be classified as a neutrophilic vasculitis targeting the vasa vasorum. Aneurysm formation may be related to degeneration of arterial wall caused by inflammation of the vasa vasorum.