Cellular and molecular dynamics in exercise-induced urticarial vasculitis lesions

Based on the histologic findings of fully developed lesions, leukocytoclastic vasculitis has been regarded as the histologic criterion for differentiating urticarial vasculitis from urticaria. Nevertheless, because the early lesions have not been examined histologically, the key biological events leading to the development of leukocytoclastic vasculitis remain unknown. To address this issue, urticarial vasculitis lesions induced by physical exercise were sequentially examined histologically and immunohistochemically in a patient over the course of 24 hours. Serum levels of various cytokines also were determined in parallel.

At 3 hours after exercise challenge, the number of identifiable mast cells decreased and the first cell type that appeared around the vessels was the eosinophil. The serum tumor necrosis factor alpha level was strikingly increased as compared with that before challenge. Intense expression of E-selectin was also induced at 3 hours. The deposition of eosinophil peroxidase was observed at 3 hours and reached maximum deposition at 10 hours. The eosinophil peroxidase deposits preceded the prominent influx of neutrophils and the subsequent deposits of neutrophil elastase.

The extracellular deposition of eosinophil granule proteins, in addition to the deposition of immune complexes and a variety of cytokines from the infiltrating cells, appears to be one of the key biological events that determines whether urticarial lesions resolve without causing vasculitis or develop into vasculitis.