Immunohistochemical and immunopathologic characterization of superficial stromal immune-mediated keratitis in horses.

The study aimed to understand the immunopathologic characteristics of a disease known as superficial stromal immune-mediated keratitis (IMMK) in horses. The researchers analyzed specific immune cells and antibodies in the corneas of 10 horses affected by IMMK. They found that cell-mediated inflammation from two types of T cells dictates the pathogenesis of IMMK, supported by the presence of local immunoglobulins. However, antibodies binding to the cornea were not detectable in the animals’ serum or aqueous humor.

Methodology

• The research involved 10 client-owned horses that had been diagnosed with IMMK.
• Immunohistochemical staining was conducted on keratectomy (corneal tissue) samples from 10 horses using antibodies. These antibodies targeted T-cells (CD3), B-cells (CD79a), Helper T-Cells (CD4), and Cytotoxic T-Cells (CD8).
• The researchers also used antibodies that react with equine immunoglobulin (IgG, IgM, IgA) to identify its presence in the cornea of these horses.
• They collected serum and aqueous humor (a transparent fluid in the eye) samples from 3 horses to test for the presence of these corneal-specific antibodies.

Results

• The results revealed a significantly greater incidence of T-cells (CD3) compared to B-cells (CD79a).
• All samples tested positive for both Helper (CD4) and Cytotoxic (CD8) T-cells, but there was no significant difference between their concentrations.
• All corneal tissue samples stained positively for immunoglobulins IgG, IgM, and IgA, indicating their presence at the affected sites.
• None of the serum or aqueous humor samples from horses with IMMK reacted with unaffected horse cornea, suggesting that these corneal-binding antibodies were not present in the serum or aqueous humor of horses with this disease.

Conclusions

• The research concluded that the pathogenesis of superficial stromal IMMK involved inflammation driven by both helper and cytotoxic T-cells.
• While local immunoglobulins were detected in the corneas of affected horses, the study found no evidence of corneal-binding antibodies in either the serum or aqueous humor of horses with IMMK.