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Conference abstract - Peer-reviewed, 2004

“Cytokine mRNA expression as a marker of inflammation in bronchial tissues in horses with RAO.”

Eva, Wattrang; Riihimäki, Miia; Pringle, John


The aim of this study was to evaluate the use of RT-PCR-techniques on endobronchial biopsy samples for detection of cytokine mRNA in studies on equine airway inflammation. Five horses with Recurrent Airway Obstruction (RAO, heaves), defined by compatible clinical examination and history coupled to markedly elevated bronchoalveolar lavage (BAL) neutrophils, and five healthy controls with normal BAL cytology were included in this pilot study. All horses were examined during the stabling period and received detailed clinical and respiratory examinations, including auscultation following rebreathing, routine blood sample analysis for white and red blood cell parameters, including fibrinogen, arterial blood gas partial pressures and pH, upper and lower airway endoscopy, and bronchoalveolar lavage and bronchial biopsy samples under endoscopic guidance. RNA from bronchial epithelium and BAL cells obtained from each horse was examined for expression of IL-6 and IL-12 p40/IL-12p35 mRNA using RT-PCR. All horses with RAO showed expression of IL-6 mRNA in biopsies and BAL-samples, whereas two (biopsy and BAL) controls showed clear IL-6 mRNA expression, with a third control positive only on BAL. IL-12 mRNA expression showed a partially different picture, where IL-12 p35 mRNA seemed constitutively expressed in all horses in both biopsies and BAL-samples. However, IL-12p40 mRNA was expressed in BAL of all horses except one of the RAO group, whereas only two of the RAO affected horses versus three of the control horses expressed IL-12p40 mRNA in the biopsy samples. Curiously, the cytokine mRNA expression thus indicated airway inflammation in some of our “normal” control horses from conventional stables, despite the lack of neutrophil response in BAL. A correlation between biopsy and BAL samples regarding mRNA expression of the cytokines evaluated was also observed. Further studies with different cytokines are needed to explain why horses react differently in the same environment. Biopsies from healthy horses after the pasture period are currently being examined to use as an additional control material. These results indicate that cytokine mRNA expression in biopsy samples may be a valuable tool in studies of equine inflammatory airway diseases. Major funding for this project was through grants from the Swedish Horse Racing Totalizator Board (ATG), with partial support from AGRIA animal insurance


Clinical Immunology and Immunopathology; Cytokines and Chemokines; Equine

Published in


IVIS-Congress, International Veterinary Immunology Society 25-30/7-2004