Total protein and immunoglobulin concentrations in equine tears

Lacrimal fluid represents a major ocular surface defensive mechanism providing different concentrations of all immunoglobulin classes. In this report, four classes of immunoglobulins (IgA, IgM, IgG and IgGT) have been measured in horse tears. As in others species, IgA is the main immunoglobulin responsible for local protection and constitutes quantitatively, 50% of all lacrimal proteins. The rest of immunoglobulins studied are normally present in equine tear fluid (though in lower concentration) and contribute to ocular surface immune protection. Female and adult horses showed significant higher mean IgA concentration than male and young horses. The lack of a significant correlation between plasma and tear immunoglobulin level suggest the presence of active transport or secretion mechanisms similar to that reported for IgA in other species.