ABSTRACT
It has been postulated that chronic actinic dermatitis (CAD), an eczematous photodermatosis, is a type IV hypersensitivity reaction. Expression of adhesion molecules on dermal blood vessels is critical to the recruitment of inflammatory cells into the skin; the pattern and kinetics of upregulation of these molecules in the skin differ following ultraviolet irradiation and delayed hypersensitivity reactions. We therefore investigated the kinetics of expression of endothelial leucocyte adhesion molecules (E-selectin) vascular-cell adhesion molecules 1 (VCAM-1) and intercellular adhesion molecule 1 (ICAM-1) in CAD lesions induced by suberythemal solar-stimulated radiation, by immunohistochemical staining of biopsies taken at 1-168 h after irradiation. In control, unirradiated skin from CAD patients, baseline vessel-associated and interstitial ICAM-1, and vessel-associated VCAM-1 were noted; focal keratinocyte ICAM-1 expression was observed in two of the five patients. Endothelial E-selectin, and vessel-associated and interstitial VCAM-1 expression, were upregulated in induced lesions by 1-5 h in all patients, and remained elevated at 120-168 h. Vessel associated, dermal interstitial, and keratinocyte ICAM-1 expression was upregulated in all patients at 24 h, and remained increased at 120-168 h. These findings differ from those observed following ultraviolet irradiation of normal skin, and resemble those seen in normal skin during a delayed-type hypersensitivity reaction, supporting the hypothesis that CAD involves a type IV response to an as yet unidentified photo-induced antigen.
