Objective: Human corneal cells have detectable levels of TLRs 1-10. TLRs 2 and 4 are the major corneal receptors, recognizing the PAMPs associated with fungal invasion in humans. The conjunctiva and limbus contain TLRs 2, 4, and 9. Our purpose was to determine the expression of TLRs 2, 3, 4, 6, 9, and MD-2 in the normal equine cornea, conjunctiva, and limbus.
Methods: Corneal, limbal, and conjunctival tissues were collected from seven euthanized horses having no evidence of ocular disease. RNA extraction with DNase-1 digestion was performed followed by RT-PCR to determine expression of TLRs 2, 3, 4, 6, 9, and MD-2. Products were resolved by electrophoresis on 1.5% agarose gels and visualized using ethidium bromide staining.
Results: Expression of TLRs 2, 3, 4, 6, 9, and MD-2 was present in the cornea, limbus, and conjunctiva of each horse, except one horse, where TLR3 expression was unable to be demonstrated in the dorsal and ventral conjunctiva.
Conclusions: Confirming the expression of TLRs in equine ocular tissues is an initial step in identifying how they play a role in infectious keratitis, particularly fungal. The results further support the use of equine ocular tissues as a model for human fungal keratitis. Studies of the TLR expression together with their cytokine profile induced during equine fungal keratitis may help further clarify the pathogenesis of the disease and possibly lead to the development of new treatment protocols for both equines and humans.
© 2011 American College of Veterinary Ophthalmologists.