Immunopathology of the uveitis in canine leishmaniasis

Particular immunopathological features and their effects on the vascular permeability of different ocular structures were analysed in two dogs naturally infected by Leishmania infantum. The existence of specific anti-Leishmania immunoglobulin G (IgG) in the aqueous humour was confirmed by the ELISA technique. There was no correlation between antibody levels in the aqueous humour and the related serum. The histopathological study of the eyes showed the existence of lesions in various ocular structures. The ciliary processes, ciliary body, sclerocorneal limbus, iris and lacrimal duct showed intense inflammatory zones with lymphocyte infiltrates, plasmatic cells and macrophages with amastigote forms of Leishmania. In addition vasculitis with dilation and thrombi were also detected in both cases, with consequent oedema and hyalinization. The immunohistochemistry analysis revealed the presence of granular and diffuse IgG deposits in the ciliary body, ciliary processes, sclerocorneal limbus and iris. Furthermore, numerous thrombosed vessels were observed in the sclerocorneal zone and iris. Complement 3 (C3) fraction deposits were not present in the ocular structures. The present data suggest that the ocular lesions may have an immunopathological origin.