Immunohistochemical investigation of the distribution of immunoglobulins G, A and M within the anterior uvea of the normal equine eye.

The research investigates the presence and distribution of immunoglobulin classes G, A, and M in various parts of the equine eye with no apparent disease. The study finds such immunoglobulins present in specific areas of the eye, mainly in the ciliary processes and ciliary epithelium, but not in the iris stroma.

Methodology

• The study investigated the distribution of immunoglobulin (Ig) subclasses – G, A, and M in the anterior uvea of eight clinically normal equine eyes.
• This investigation used indirect immunoperoxidase labelling — a method where an antibody conjugated with a peroxidase enzyme binds to targeted antigens to provide visual matching.

Findings

• The study observed increased staining of IgG and IgA in the stromal tissue of the ciliary processes, indicating a considerable presence of these Igs in this part of the equine eye.
• The iris stroma, however, was mainly free of any immunoglobulin.
• Such distribution patterns suggest that there are anatomical differences in how uveal microvasculature allows lipids insoluble plasma macro-molecules to pass.

Intracellular Presence

• Furthermore, the study found intracellular IgG and IgA within the non-pigmented ciliary epithelium.
• The presence of these Igs varies across the eight samples, with seven eyes showing intracellular IgG and four eyes showing intracellular IgA.
• The findings suggest these cells potentially have a role to play in removing Ig from the posterior chamber’s fluid.

Absence of Intraocular Ig Production

• The study only observed plasma cells, specifically of IgG isotype, in one of the eight eyes.
• This observation leads the researchers to propose that the intraocular production of immunoglobulins is not typical in healthy equine eyes.