The effect of topical retinoic acid (Etretinate) on mouse conjunctival Langerhans cells

Four groups of BALB/c mice were treated locally with different concentrations (0.1-1.0%) of retinoic acid (Etretinate) ointment for a period of one to four weeks. A fifth group was treated with the ointment base only. Ia-positive dendritic cells were identified by an indirect immunofluorescence technique which was confirmed by ADPase staining. Quantitative counts of Langerhans cells were performed for each group. After four weeks, the 0.1 and 0.2% Etretinate-treated conjunctiva showed no significant reduction in Langerhans cell concentration. However, following 0.5 and 1.0% Etretinate treatment for four weeks, the concentration of Langerhans cells was significantly reduced, and the cells showed morphologic changes, consisting mainly of loss of dendritic processes. Between one and two weeks of therapy at these two high concentrations, no significant changes were found. Light microscopy of the conjunctival epithelium showed marked atrophic changes following four weeks of 0.5 and 1.0% Etretinate treatment compared to no changes with 0.1 and 0.2% Etretinate treatment.