Immunohistochemical staining of immunoglobulin G in healthy equine, canine, and feline corneas

Abstract

Objective: Establishing an immunohistochemical approach for semi-quantitative assessment of the presence of immunoglobulin G (IgG) in equine, canine, and feline corneas. Procedures: Healthy corneas of horses, dogs, and cats, euthanized because of a fatal disease or an unrecoverable trauma unrelated to and without a history of ophthalmic disease were formalin-fixed, paraffin-embedded, and determined to be pathomorphologically healthy by light microscopy. Automated immunohistochemistry was performed using primary antibodies against IgG, biotin-conjugated secondary antibodies, and streptavidin-peroxidase, as well as diaminobenzidine for visualization. After counterstaining with hematoxylin, epithelium, stroma, Descemet´s membrane (DM), and endothelium were semi-quantitatively scored for the presence of IgG on a 4-grade scale (0 = no, 1 = faint, 2 = medium, 3 = strong staining) by light microscopy. Results: Corneal specimens of 20 horses (40 eyes) with a median age of 15.5 years (range 2–31 years), 12 dogs (21 eyes) with a median age of 10.0 years (range 4–16), and 13 cats (24 eyes) with a median age of 10.0 years (range 2–18) were included in the study. Different sexes and breeds were represented. In all corneas (100%), significant medium signal intensity in the stroma was observed. Variable immunosignal was obtained in epithelium, DM, and endothelium. Conclusion: This method reproducibly allows for the detection of IgG in healthy equine, canine, and feline corneas, particularly stroma. Semi-quantitative results evidence medium presence of IgG in the corneal stroma. Further research is needed to evaluate IgG presence in diseased corneas.