Immunoglobulin levels in tears and aqueous humor of horses before and after diethylcarbamazine (DEC) therapy.

This study investigates the concentration levels of particular types of immunoglobulins (IgGa, IgM, IgA, IgG(T)) in the tears and aqueous humor of healthy and infected horses. It specifically notes marked increases in certain immunoglobulins in infected horses treated with Diethylcarbamazine (DEC), and suggests that this may be implicated in the development of eye inflammation and corneal opacity.

Immunoglobulin levels in equine tears and the aqueous humor

• The study begins with a quantitative investigation of the levels of several different immunoglobulins (IgGa, IgM, IgA, IgG(T)) in the tears and aqueous humor of horses. The aqueous humor is the fluid in the front and rear chambers of the eye, while tears are the fluid produced by the tear glands.
• The horses used in the study were a mix of normal and infected animals. The infected horses had a (parasitic infection Onchocerca cervicalis), which is common in horses.
• The researchers used two techniques to measure the levels of these immunoglobulins: single radial immunodiffusion (SRID) or radioimmunoassay (RIA). These are common laboratory techniques used to measure the concentration of specific substances in a sample.

Perturbations in immunoglobulin levels following DEC treatment and infection

• In horses with eye inflammation, the level of one of the immunoglobulins (IgGa) was found to be 18 times higher in tears. The researchers suggest this could be due to both the eye inflammation itself and the treatment with Diethylcarbamazine (DEC), a medication used to treat parasitic infections.
• Parasite-infected animals treated with DEC showed marked elevations in certain immunoglobulins (IgGa and IgG(T)) in both the tears and aqueous humor.
• Notably, these changes were observed prior to the development of visible corneal abnormalities (corneal opacities) in the infected horses. Corneal opacities are a common symptom of ocular diseases and can affect the horse’s vision.

Interpretation of findings

• The researchers caution that the observed increases in the aqueous humor may not be a direct consequence of the DEC treatment or infection, but might instead be due to the invasive nature of the sampling method (paracentesis). This procedure involves puncturing the eye to obtain a fluid sample and can cause inflammation.
• The researchers also note that the precise contribution of specific antibodies against the parasite (antimicrofilarial antibodies) remains uncertain. However, these antibodies may account for a significant proportion of the total immunoglobulins detected in the tears.