EPIDERMAL IMMUNOCOMPETENCE IN CANINE LEISHMANIASIS

The antigen-presenting cell function of the epidermis was investigated immunocytochemically in 16 dogs with different types of skin lesions induced by Leishmania infection. The degree of epidermal immunocompete nce was evaluated according to the presence of Langerhans cells (LC) a nd keratinocytes expressing class II major histocompatibility complex (MHC II) molecules on the one hand, and the relative numbers of macrop hages, T cells, and parasites in the dermis on the other, as described for human cutaneous leishmaniasis. In alopecic dermatitis, appropriat e numbers of LC and MHC II-positive keratinocytes were shown to be ass ociated with a mild T cell infiltration without significant numbers of parasites. By contrast, when the epidermis lacked antigen-presenting cells, as occurred in nodular lesions, macrophages and parasites massi vely infiltrated the dermis. Ulcerative lesions showed intermediate pa tterns of inflammation. These results suggest that dogs with alopecic dermatitis develop an effective control of the infection, whereas thos e with a generalized nodular disease mount an impaired immune response against the parasite. Skin lesions in dogs infected by Leishmania mig ht not only have a prognostic value, but also represent a suitable mod el to study the natural course of human cutaneous leishmaniasis. (C) 1 997 Elsevier Science B.V.