Differential Effects of Structurally Unrelated Chemical Irritants on the Density and Morphology of Epidermal CD1+Cells

In order to gain a greater insight into the complex mechanisms of action of different irritant chemicals on the skin, we have studied the behavior of epidermal CD1 + cells in experimentally induced irritant contact dermatitis. Healthy, human volunteers were patch tested for 48 h with the following six chemically unrelated irritants and their appropriate vehicle controls; benzalkonium chloride, sodium lauryl sulphate, dithranol, nonanoic acid, croton oil, and propylene glycol. After visually assessing and grading the resulting inflammatory reactions, punch biopsies were taken and the morphology and density of CD1+ cells in the epidermis studied using immunocytochemical techniques in combination with image analysis and electron microscopy. Statistically significant decreases in the epidermal density of CD1 + cells occurred in the responses to dithranol (p < 0.05) and nonanoic acid (p < 0.01). Importantly, these changes in density were not simply due to variations in the intensity of inflammatory response (r = 0.1157). Alterations in the length of the dendritic processes of CD1 + cells were also induced, and semi-quantitative analysis revealed significant decreases in dendrite length in the reactions to sodium lauryl sulphate (p < 0.05), nonanoic acid (p < 0.001), croton oil (p < 0.05), and dithranol (p