T and B lymphocytes, macrophages and Langerhans' cells during the course of contact allergic and irritant skin reactions in man.

The in situ distribution of lymphocyte subclasses, macrophages and Langerhans' cells was analysed with histochemical (ANAE staining), immunohistochemical (immunoperoxidase) and electron microscopic methods during the course of epicutaneous allergic and irritant skin reactions. Serial biopsies were taken during the first 5-72 hours following the allergen (nickel and chromium) or irritant (non-anoic acid and dithranol) application. Empty and petrolatum-filled Finn chambers were used as controls. No significant differences in the number of mononuclear inflammatory cells or their subclasses were found in the early recognition and elicitation phases of the allergic or irritant-induced reactions. Nor was there any difference in the frequency of lymphocyte-Langerhans' cell contacts, although exocytic cells were most frequent in dithranol reactions.