Extracellular deposition of eosinophil granule major basic protein in pressure urticaria

Utilizing affinity chromatography-purified antibody to the eosinophil granule major basic protein and formalin-fixed paraffin embedded tissue, we investigated the localization of major basic protein by immunofluorescence in twenty-four skin biopsy specimens from ten patients with pressure urticaria. Fourteen of twenty-four biopsy specimens were obtained from spontaneously occurring urticarial lesions of 4 to 48 hours' duration, and ten of the twenty-four specimens were from dermographometer-induced lesions that had been present from 40 minutes to 24 hours. Twenty-one of twenty-four biopsy specimens showed extracellular fluorescence of eosinophil granule major basic protein within the dermis. The extent and intensity of extracellular staining were not related to the presence or degree of tissue eosinophilia. Serial section controls from each block were stained with protein A purified rabbit IgG and were negative. Previous immunofluorescence studies have demonstrated deposition of major basic protein in lesions of chronic idiopathic urticaria, episodic angioedema, and facial edema. Major basic protein causes release of histamine from human basophils and induces wheal-and-flare reactions on intradermal injection. The present observations add further evidence to support a role for eosinophil mediators, particularly major basic protein, in the pathogenesis of cutaneous disease characterized by edema.