Phenotypic characterization in situ of inflammatory cells in allergic and irritant contact dermatitis in man.

The cellular response in allergic and irritant contact dermatitis was analysed in situ with an immunohistochemical double staining technique. Allergic patch test reactions were elicited in 10 patients and irritant reactions in eight cases, using the Finn chamber technique. Skin biopsies were obtained 6-72 h after test applications. Frozen sections of 43 biopsies were investigated by simultaneous staining with rabbit anti-HLA-DR antibodies and various mouse monoclonal antibodies. The cell infiltrates were usually larger in the allergic than in the irritant reactions. However, the kinetics of the cell responses, the phenotypes of the inflammatory cells, their distribution and spatial relationships were similar. It thus appears that the applications of allergens or irritants to the skin generates a cell pattern that to a large extent reflects an immunological readiness for further immune reactions.