Immunohistochemical findings in eyes of cats serologically positive for feline immunodeficiency virus (FIV).

In this study the eyes of 15 cats in the terminal stage of FIV infection were examined. The findings were compared to those in cats, which were euthanized because of other infectious diseases for for non-infectious reasons. Thirteen FIV-infected cats showed an anterior uveitis by means of light microscopy. No accumulation of retinal lesions were found in FIV-infected cats compared to the other cats examined. Additionally, there were no indications of lesions caused by opportunistic infections. In the posterior segments of the eyes, immunohistochemical examinations proved the plasma proteins C3 and IgG to be predominantly intravascular. The eyes of 11 serologically FIV-positive cats were available for immunohistochemical examination. In all 11 cats at least one of the plasma proteins C3 or IgG could be detected in the extravascular tissue of the anterior uvea. The extravascular presence of plasma proteins within the tissue seemed to be caused by an increased permeability of the vessels due to inflammation. Furthermore, the similar extravascular distribution pattern of IgG and complement component C3 in four cases indicated that immune complexes may play a role in the anterior uveitis of FIV-infected cats.