Résumé : Frozen skin biopsies from 3 acute and 3 chronic lesions of atopic dermatitis were examined by means of various ortho-monoclonal antibodies (OKT3, 4]=⇐4, OKT6, OKT8; OKIa and OKM1) in an indirect immunofluorescence technique. The results show that both T helper (T4) and T suppressor cytotoxic (T8) lymphocytes are present in the inflammatory infiltration which predominantly contained Ia mononuclear cells. Despite the absence of double staining procedure, the observations suggest that T4 cells predominate over T8 cells in the acute lesions whereas the reverse tendency is noted in the chronic lesions. T8 cells are found mainly in the superficial dermis or even in the epidermis; by contrast, T4 cells tend to be more deeply located in the dermis. The lesions are characterized by a dramatic increase in the number of Langerhans cells (OKT6, OKIa+) that are found not only in the epidermis but also in the dermis. © 1984 S. Karger AG, Basel.