Epidermal proliferation and keratinization following standardized elicitation with diphenylcyclopropenone

Keratin 17 is expressed during the course of SLS-induced irritant contact dermatitis, but unlike keratin 16, the degree of expression is unrelated to the density of dividing keratinocytes

The aims of this study were to utilize quantitative immunocytochemical techniques to determine the densities of keratin 16 (K16) and keratin 17 (K17) expressed by keratinocytes during the course of acute patch test reactions to sodium lauryl sulfate (SLS), and to relate these to the proliferative state of the epidermis, as assessed by Ki-67 immunolabelling. Significantly increased numbers of dividing keratinocytes were present in 48h and 96h reactions, concurrent with high levels of expression of K16 and more moderate expression of K17. Statistical analysis indicated a good correlation between K16 expression and the density of Ki-67+ keratinocytes present in the epidermis (r=0.843). This was not the case for K17 (r=0.396). The results demonstrate that both K16 and K17 expression are features of acute irritant contact dermatitis reactions, but suggest that the factors which influence and control their expression differ.

Changes in epidermal proliferation and differentiation in allergic and irritant contact dermatitis reactions

Allergic and irritant contact dermatitis are similar clinically, histologically and on immunohistochemistry. In the present investigation, we assessed whether study of the recruitment of cycling epidermal cells, and the expression of keratin 16 and involucrin, are of use in differentiating between the response to contact allergens and the response to the irritant detergent sodium lauryl sulphate. Both allergic and irritant challenges induced epidermal proliferation, and the expression of keratin 16 and involucrin, but the dynamics were different. Two and 3 days after challenge, a highly significant difference between the allergic and irritant reactions was observed with respect to involucrin expression assessed by MON-150 staining.