Histological and immunohistochemical evaluation of canine chronic superficial keratitis.

Chronic superficial keratitis (CSK) is an inflammatory disease of the canine cornea, characterised by infiltration of leucocytes into the anterior corneal stroma. The present study describes a quantitative histomorphometric analysis of the cell types infiltrating the corneal stroma in this disease. Infiltrating cells were quantified in samples taken at superficial keratectomy and processed for routine histology. Further characterisation of lymphocyte phenotypes was achieved by immunohistochemistry performed using a panel of monoclonal antibodies recognising canine lymphocyte CD antigens. Lymphocytes expressing the CD4 antigen were found to be the predominant infiltrating cell types in the CSK lesion. A significantly smaller number of lymphocytes expressed the CD8 antigen. The CD4/CD8 ratio was consistently above 2 and rose to above 4 at the advancing border of the lesion. A proportion of lymphocytes were shown by immunohistochemistry to contain gamma interferon. This study forms a basis for work further evaluating the cytological events central to the development of this spontaneous potentially auto-immune corneal disease.