Ultrastructural aspects of infiltrated eosinophils in bullous pemphigoid.

By scanning (SEM) and transmission electron microscopy (TEM), we evaluated the infiltrated eosinophils in lesions at various stages of clinical development from patients with bullous pemphigoid (BP) and eosinophilia. Visualized by SEM, numerous inflammatory cells migrated through the cutaneous basement membrane into the cavity of newly formed blisters 12 to 24 hrs after formation. Many migrating cells attached to the reverse side of the bullous cavity, and some basal cells shed into the cavity. As the bullae developed 24 to 48 hrs after formation, the reverse surface of the bullous cavity became predominantly composed of these migrating cells and the exposed squamous cells. The migrating cells had villi, ruffles and ridge-like profiles on their surfaces, which were suggested eosinophils. By TEM in the same lesions, many morphologically activated eosinophils were seen to have passed through the basement membrane into the newly formed blisters; they exhibited spheroidal cytoplasmic granules with less dense crystalloid cores and intracellular channels. Eosinophils infiltrating in the developed bullous cavity directly adhered to basal cells and released their granule contents onto these target cells. These findings suggest that inflammatory cells, especially eosinophils, may amplify the formation of dermal-epidermal separation in BP lesions.

Eosinophil phenotypes in bullous pemphigoid.

Eosinophil phenotypes were investigated in peripheral blood and skin lesions from eight patients with bullous pemphigoid (BP). By Nycodenz density gradients fractionation, blood eosinophils were divided into two phenotypes; normodense (greater than 1.080 g/ml) and hypodense (less than or equal to 1.080 g/ml). Increased numbers of hypodense eosinophils were observed in the blood from all patients with BP. Immunocytochemical observations, using an EG2 monoclonal antibody to react with the secretion form of eosinophil cationic protein (ECP), revealed that EG2 was expressed in 86 +/- 3% of hypodense phenotypes and 3 +/- 2% of normodense phenotypes. Ultrastructurally, hypodense eosinophils were characterized by numerous spheroidal granules, each with a lytic crystalloid core. These indicate that the hypodense phenotype represents a cell in an activated state. Only eosinophils with immunocytochemical and morphological characteristics similar to hypodense phenotypes infiltrated around the basement membrane zone in involved skin of BP. Furthermore, direct adherence of eosinophils associated with degranulation into basal keratinocytes was seen at the sites of blistering lesions. Bullous fluids contained higher concentrations of ECP than sera as determined by a radioimmunosorbent assay; thus hypodense (activated) eosinophils may directly damage the basal keratinocytes by releasing their granule proteins, subsequently leading to dermo-epidermal separation.

Alteration in the density, morphology, and biological properties of eosinophils produced by bullous pemphigoid blister fluid.

Bullous pemphigoid blister fluid (BP-BF) was examined for its effects on the density, morphology, and biological properties of eosinophils. Normodense eosinophils (NEo) were prepared from guinea pig peritoneal exudates by Nycodenz density gradient centrifugation. After culturing with BP-BF, NEo were converted into hypodense eosinophils (HEo) in a time-dependent manner. HEo were morphologically different from NEo in that HEo had spheroidal granules each with a lytic crystalloid core and a significantly increased cell volume. These HEo showed an enhanced antibody- and/or complement-dependent helminthotoxic activity to Schistosoma mansoni larvae, amplified chemiluminescence response to opsonized zymosan, and augmented expression of both FcR+ and CR+. These results suggest that BP-BF contains an activity that may not only induce an eosinophil hypodensity as a consequence of increasing cell volume, but simultaneously enhance an eosinophil cytotoxic potential through augmenting cell-surface receptors and receptor-linked oxidative metabolism. In addition, observed tissue accumulation of this activity suggests that eosinophils may be regulated by their phenotypic change in the skin lesions of bullous pemphigoid and be involved in blister formation.