Langerhans cells in acute and chronic epidermal lesions of atopic dermatitis, observed by L-dopa histofluorescence, glycol methacrylate thin section, and electron microscopy

Since epidermal Langerhans cells are known to play an immunopathologic role in allergic skin diseases, we explored the histological features of Langerhans cells associated with epidermal lesions in acute and chronic stages of atopic dermatitis. The L-dopa histofluorescence method, introduced by Falck and others in 1976, has provided a new approach to visualization of Langerhans cells in normal and pathologic skin of both experimental animals and human beings. We used this technique for skin biopsy specimens from normal individuals and patients with atopic dermatitis. We also used embedding of thin sections in glycol methacrylate, electron microscopy, and autoradiography of ³H L-dopa to observe morphological characteristics of Langerhans cells in these skin specimens. We observed a few Langerhans cells in the spongiotic epidermis of acute erythematous lesions, but many fluorescent infiltrating mononuclear cells were also present in both epidermal and subepidermal layers. In chronic lichenified lesions significantly increased numbers of Langerhans cells were distributed throughout acanthotic epidermis, but the numbers of infiltrating mononuclear cells in the epidermis were greatly reduced. Focal accumulations of both Langerhans cells and monocytic cells were occasionally found in the epidermis of chronic lesions; these accumulations are thought to be recurrent inflammatory foci in the chronic lesions. The use of L-dopa histofluorescence to study epidermal Langerhans cells demonstrates Langerhans cells more clearly than other histological means.