Quantification of antigen-specific antibody concentrations in tracheal lavage fluid of horses with summer pasture-associated obstructive pulmonary disease

Objective-To determine whether horses with summer pasture-associated obstructive pulmonary disease (SPAOPD) have increased concentrations of antigen-specific IgG and IgE in tracheal lavage fluid, compared with values in clinically normal horses. Animals-8 horses (6 females, 2 geldings; 6 Quarter Horses, 2 Appaloosas), 14 to 23 years old and with previous diagnosis of SPAOPD, served as the principal group; 8 horses (2 females, 6 geldings; 1 Quarter Horse, 7 Thoroughbreds), 6 to 9 years old, with no evidence of respiratory tract disease, served as the control group. Procedure-Data were collected twice during a 1-year period: when all SPAOPD-affected horses were manifesting clinical signs of disease (July), and when all SPAOPD-affected horses appeared clinically normal (February). On each occasion, clinical evaluations were performed and blood and tracheal ravage fluid samples were collected. Transtracheal lavage supernatant was evaluated for mold antigen-specific IgG and IgE concentrations. Results-Median IgE relative antibody unit (RAU) values were significantly higher in control, compared with principal, horses. The SPAOPD-affected horses had increased concentrations of specific IgG for only 1 antigen, during winter sample collection. Conclusion-Antigen-specific IgG and IgE RAU values were not increased in SPAOPD-affected horses when these horses were manifesting clinical signs of disease.