Chronic exacerbation of equine heaves is associated with an increased expression of interleukin-17 mRNA in bronchoalveolar lavage cells.

The research article focuses on the investigation of a potential role of Interleukin (IL)-17, a type of protein, in the development of chronic respiratory condition known as ‘heaves’ in horses.

Overview of the Study

• This study was aimed at understanding the role of T-cells, which play a significant part in the immune response, in the pathogenesis or development of heaves in horses. Specifically, the researchers were interested in a cytokine (a type of protein that could influence immune response) called Interleukin-17, or IL-17, which is known to stimulate and enable neutrophils—white blood cells key to immune defense mechanisms.
• The scientists’ primary hypothesis was that IL-17 could be a significant factor in the recruitment of neutrophils to the airways, contributing to the development of heaves in horses. The study was specifically designed to measure and compare the expression of IL-17 in affected and unaffected horses.

Design and Findings of the Study

• Four horses susceptible to heaves and four control horses were examined when in pasture (during clinical remission), and after being exposed to moldy hay for 35 days, a known trigger for the condition.
• Measurements of respiratory mechanics and Bronchoalveolar Lavage (BAL)—a procedure which involves washing the bronchus and collecting the fluid for analysis to understand lung disease—were carried out during both periods of the study.
• The team used a real-time Polymerase Chain Reaction (PCR), an essential tool in medical and biological research to amplify and quantify DNA, to check the expression of mRNA (messenger RNA), which helps to produce proteins, for IL-17 in the BAL fluid. The amount of CD3-zeta, a marker for T-cell numbers, was also determined for comparison.
• No significant difference in IL-17 mRNA expression was noticed between the two groups while in pasture. However, exposure to moldy hay resulted in increased IL-17 mRNA expression in all heaves-prone horses, but not in any of the control horses.

Research Insights

• This suggests that an increase in IL-17 mRNA expression may contribute to the pathogenesis of heaves in horses that continuously encounter certain antigens or foreign substances, like moldy hay, that provoke immune responses. Consequently, IL-17 can potentially be a target for treatment strategies.
• The findings from the research are preliminary and offer a foundation for more extensive studies in the future to understand further and confirm IL-17’s role in the pathogenesis of heaves.