Cellular events leading to blister formation in bullous pemphigoid

Cellular events occurring in eight patients with bullous pemphigoid were studied by light and electron microscopy. Sections (0.5 micrometer) of large surface area, overlapping blisters and surrounding skin, were examined and correlated ultrastructural studies were performed on selected areas. The peroxidase contained in granules of neutrophils, eosinophils and young macrophages was visualized by incubation with diaminobenzidine and hydrogen peroxide. This cytochemical reaction was used as a marker to study the release of granule enzymes from these inflammatory cells. The release of such enzymes from eosinophils and occasionally from macrophages on the epidermal basement membrane (more precisely in the lamina lucida) was demonstrated in the skin surrounding the blisters in four patients. The release of these enzymes was also observed in the floor of the blisters in all eight patients. It is well known that these granules contain several proteolytic enzymes. These observations are therefore consistent with the proposal that proteolytic enzymes of eosinophils play a pathogenic role during the initial stages of blister formation in bullous pemphigoid.