Bronchoalveolar Lavage Fluid Cytology and Cytokine Messenger Ribonucleic Acid Expression of Racehorses with Exercise Intolerance and Lower Airway Inflammation

Abstract

Background: There is limited information relating bronchoalveolar lavage (BAL) cytology and cytokine messenger ribonucleic acid (mRNA) expression in racehorses with inflammatory airway disease (IAD). Hypothesis and Objective: We hypothesize that cytokine expression in BAL cells would correlate with cytology. Thus, we evaluated the mRNA expression of selected cytokines in BAL cells in racehorses with exercise intolerance and lower airway inflammation. Animals: Thirty-one client-owned Standardbred racehorses with exercise intolerance. Methods: Prospective, observational study. Cells were obtained by BAL, and mRNA expression of interleukin (IL)-1β, IL-4, IL-8, tumor necrosis factor (TNF)-α, and interferon (IFN)-γ was determined by reverse transcription quantitative polymerase chain reaction (RT-qPCR). Results: Nine horses had normal BAL cell differential cytology (Controls), while 22 horses had evidence of IAD based on BAL fluid cytology. Relative expressions of TNF-α/glyceraldehyde 3-phosphate dehydrogenase (GAPDH; 0.0092 ± 0.010 versus 0.0045 ± 0.005, P=.034), IL-4/GAPDH (0.001 ± 0.002 versus 0.0003 ± 0.0003, P=.029), and IFN-γ/GAPDH (0.0027 ± 0.003 versus 0.0009 ± 0.001, P=.028) were greater in horses with IAD compared with controls. Furthermore, IL-4/GAPDH (0.001 ± 0.002 versus 0.0002 ± 0.0003, P