Activation of Fc epsilon RI-positive eosinophils in bullous pemphigoid

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, Fc epsilon RI, 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 Fc epsilon RI-positive cells in all cases. These cells were not detected in the epidermis, and examination of mirror sections confirmed that the Fc epsilon RI-positive cells corresponded to eosinophils. It has been demonstrated that Fc epsilon RI-positive cells are involved in the dermal lesions of BP. The activation of eosinophils by Fc epsilon RI may participate in the pathogenesis of BP by triggering the degranulation of mast cells.