MORPHOLOGICAL FEATURES OF OCULAR INFLAMMATION AND DISTRIBUTION OF VIRAL ATIGENS IN THE OCULAR TISSUES OF CATS WITH FELINE INFECTIOUS PERITONITIS (FIP)
N. Ziółkowska1, B. Lewczuk1, K. Paździor-Czapula2, E. Mikulska-Skupień3
Department of Histology and Embryology1, Department of Pathological Anatomy2, Department of Epizootiology3, Faculty of Veterinary Medicine, University of Warmia and Mazury, Olsztyn, Poland
Purpose: The study was performed to characterized the ocular lesions in cats with feline infectious peritonitis using histological and immunohistochemical methods. Methods: Eyes from fifteen cats of different breeds, naturally infected with FCoV (feline coronavirus), were taken for histological and immunohistochemical studies. Before euthanasia ocular examination was performed. The eyes were fixed in formalin, dehydrated and embedded in paraffin. For histopathological studies, 5µm-thick sections were stained with Hematoxylin and Eosin or methyl-green-pyronin for plasma cell identification. Immunohistochemical examination was performed using anti-coronavirus, anti-CD3, anti-CD79 and anti-macrophages antibodies (MAC 387). Results: Lesions were found in the iris, cilliary body, choroid, retina, optic nerve, cornea, sclera and conjunctiva (Fig. 1-6), which were infiltrated by lymphocytes, plasma cells and less commonly macrophages. Immunohistochemistry revealed that among lymphocytes CD79-positive B cells were much more numerous than CD-3 positive T cells. CD3-immunoreactive cells were present within damaged cilliary processes, iris and around scleral blood vessels. Macrophages were detected between sclera and corneal collagen fibers, and in conjunctiva, choroid, retina and cilliary body. A positive reaction for FCoV was observed in macrophages present within inflammatory exudates in the posterior chamber. Conclusion: The characteristic feature of all examined eyes with signs of disease was infiltration of ocular tissues mostly by CD79-positive B cells and plasma cells. This suggests a predominance of the humoral immunity response in ocular inflammation during FIP. Damage of the ocular tissues should be considered mainly as a consequence of inflammatory processes. Direct destructive actions of the virus on cells in the eye seems to be less important.