Increased expression of eotaxin and its specific receptor CCR3 in bullous pemphigoid

Several skin infiltrating inflammatory cells, such as eosinophils, neutrophils and activated T lymphocytes, are involved in bullous pemphigoid (BP) blister formation. The presence of CD4⁺ T cells able to produce IL-4 and IL-5 suggests Th2 involvement in the disease. The role of eotaxin in the recruitment of eosinophils into inflammatory sites has been recently described and the specific eotaxin receptor, CCR3, has been documented to be expressed on eosinophils, basophils, and Th2 cells. In this study, we analyzed by immunohistochemistry the expression of both eotaxin and CCR3 in lesional skin from patients with active BP (n = 10) and control subjects affected with pemphigus vulgaris (PV) (n = 3); furthermore eotaxin concentration in BP sera and blister fluids was also evaluated by enzyme-linked immunosorbent assay (ELISA), in comparison to sera from PV and normal donors (n = 10) and to suction blisters from 3 healthy volunteers. A strong immunostaining for eotaxin and CCR3 in BP skin specimens in lesional and, to a lesser extent, in perilesional skin was observed. CCR3 expression was documented on both eosinophils and T cells infiltrating skin lesions. Eotaxin serum levels were significantly higher in BP patients when compared to healthy donors (p = 0.003) and PV patients (p = 0.01). The highest eotaxin concentration was detected in BP blister fluids, in respect to both corresponding BP sera and blister fluids from normal donors (p = 0.003). These results account for the role of eotaxin in the recruitment of activated cells at inflammatory sites during BP and the expression of CCR3 on infiltrating T lymphocytes further supports the involvement of Th2 cells in the pathogenesis of BP.