The CD11b/CD18-integrin in the pathogenesis of psoriasis.

The aim of the present investigation was to study the distribution of CD11b, CD18, and ICAM-1 over the various cell populations present in the margin zone of the actively spreading psoriatic lesion and distant uninvolved psoriatic skin. This study was performed in order to obtain more insight in the relevance of these receptor molecules in the early phase of psoriatic plaque development. Skin biopsies were taken and inflammation markers were assessed using immunohistochemical techniques. All dermal changes in the margin zone preceded those in the epidermis. In the margin zone the most peripheral change was a decrease in dermal ICAM-1-expression, followed by an increase in dermal CD11b-expression. CD11b-positive cells showed a different tissue distribution from polymorphonuclear leukocytes and were more abundantly present, suggesting significant amounts of CD11b-bearing cell populations other than polymorphonuclear leukocytes in the early phase of psoriasis. Decreased numbers of CD18-positive cells in distant uninvolved skin suggest the existence of a selective modulating mechanism altering the trafficking of myeloid subpopulations. Polymorphonuclear leukocytes appeared to invade the skin well after the appearance of CD11b- and CD18-positive cells.