Bullous pemphigoid (BP) is an autoimmune disease frequently occurring in elderly persons. It has been reported that 92-kDa gelatinase released from eosinophils cleaves the extracellular domain of BP180 protein, suggesting a direct role of eosinophils in bulla formation in this disease. The expression of the high-affinity IgE receptor, FcεRI, on eosinophils was examined in patient with BP. Samples of affected skin obtained from 7 patients with BP were stained immunohistochemically by the alkaline phosphatase anti-alkaline phosphatase (APAAP) method and mirror sections were examined. Eosinophils were present at a rate of 1.0-19.0% in lesions of the dermis, and the number of IgE-positive cells exceeded that of FcεRI-positive cells in all cases. These cells were not detected in the epidermis, and examination of mirror sections confirmed that the FcεRI-positive cells corresponded to eosinophils. It has been demonstrated that FcεRI-positive cells are involved in the dermal lesions of BP. The activation of eosinophils by FcεRI may participate in the pathogenesis of BP by triggering the degranulation of mast cells.

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