The uveitogenic potential of retinal S-antigen in horses.

This research explores the potential of retinal S-antigen to cause uveitis, an eye inflammation, in horses. Despite observable immune responses, most horses did not develop uveitis, indicating that retinal S-antigen is a weak autoantigen in horses.

Research Methodology

The researchers carried out the study on horses, which were immunized using the S-Ag, a kind of protein found in the retina, or the BSA used as a control antigen. The immunizations were done subcutaneously, that is, under the skin, and were emulsified in complete Freund’s adjuvant, a substance used to boost immune response. Additionally, the horses were simultaneously given Bordetella pertussis intravenously.

• The immune response of T and B cells to these antigens was monitored at 3-day intervals.
• The development of disease was judged both clinically and histopathologically, involving examination of cells and tissues.
• Two identical booster immunizations were given every four weeks to test whether they could cause recurrences of the disease.

Research Findings

The research findings indicated that S-Ag specific T and B cell responses were seen in all immunized horses, unlike in control animals. This means that the immune systems of the horses did recognize and react to S-Ag. But surprisingly, uveitis developed in only one of the five animals.

• Reimmunization with S-Ag in this animal did not lead to a relapse of uveitis, suggesting that the immune system did not respond in a harmful way to the antigen after the initial response.
• All other horses in both S-Ag and BSA treated groups showed neither signs of uveitis nor any inflammatory infiltrates in the inner eye.

Conclusions

The research concluded that contrary to interphotoreceptor retinoid-binding protein (IRBP), S-Ag is a weak autoantigen in horses. In other words, even though immune responses were observed, it did not lead to a condition of uveitis in most horses.

• This suggests that although S-Ag provokes an immune response, it is not strong enough to cause an inflammation of the uvea of the eye in horses.
• Even after activation of autoreactive T and B cells, intrusion of the inner eye and induction of uveitis are controlled in most horses, indicating the body’s ability to suppress an overactive immune response.