Objective: To investigate the phenotype of infiltrating cells in classic lesions of polyarteritis nodosa (PAN).
Methods: Twenty-one muscle and 10 sural nerve biopsy samples from 24 patients with systemic PAN were studied using avidin-biotin-peroxidase and alkaline phosphatase-anti-alkaline phosphatase immunohistochemical techniques.
Results: The inflammatory infiltrates consisted mainly of macrophages (41%) and T lymphocytes (41%), particularly of the CD4+ subset. Granulocytes were present in varying quantities (0-45%) and were more abundant in heavily infiltrated vessels and in those with fibrinoid necrosis. Dendritic cells could be identified in 4 samples. Proliferating and interleukin-2 receptor-expressing cells, present in 71% and 79% of the patients, respectively, were more frequent in untreated patients.
Conclusion: T cell-mediated immune mechanisms may play a role in the development and perpetuation of PAN lesions.