[Atopic dermatitis: a histologic and radioautographic study (after 3H-thymidine labelling) of epidermal and dermal lesions (author's transl)].

Skin lesions of atopic dermatitis (A. D.) have been studied histologically and radioautographically after in vitro incorporation of tritiated thymidine. The histopathologic aspects of epidermis in the different types of skin lesions are reviewed. The dermal infiltrate is mononuclear and not very abundant in all types of lesions. An enlargement of the epidermal proliferative compartment has been noticed. Labelled cells are distributed as follows (mean +/- standard deviation) : 46 +/- p. 100 in the basal layer; 37 +/- 6 p. 100 in the epibasal layer; 16 +/- 7 p. 100 in the upper layers. The basal and epidermal labelling indices have been found significantly increased in exudative and lichenified lesions as compared to xerotic areas and normal epidermis. The labelling index of the "round" cell infiltrate in the dermis was significantly higher than in irritant patch test reactions (p less than 0.001) but significantly lower than in allergic positive patch test reactions (p less than 0.001). This increased cell proliferation in the dermal infiltrate does not allow definite conclusions about immunopathogenesis of the disease: indeed, a large number of mediators, involved in the inflammatory reactions of A. D. lesions, can modulate cell proliferation.