Cytokine expression by peripheral blood neutrophils from heaves-affected horses before and after allergen challenge.

This study explores the role of neutrophils in cytokine and chemokine production that could influence inflammation and cell activation in horses with heaves, a condition marked by pulmonary neutrophilia and reversible airway obstruction. The researchers discovered that following exposure to mouldy hay, horses with heaves showed significant airway obstruction and elevated neutrophil counts, but cytokine and chemokine levels appeared unaffected, proposing that their release by peripheral blood neutrophils is not essential in the development of heaves.

Background of the Study

• Heaves, also known as recurrent airway obstruction, is a prevalent condition in horses, characterized by pulmonary neutrophilia and reversible airway obstruction.
• Neutrophils are a type of white blood cell that forms an essential part of the immune system. They release cytokines and chemokines, such as tumor necrosis factor (TNF)-alpha and interleukin (IL)-1beta, which can cause inflammation and recruit other immune cells.
• The study aimed to investigate the role of neutrophils and their production of cytokines and chemokines in the development of heaves.

Methodology

• The researchers collected peripheral neutrophils from both control (n=4) and heaves-affected horses (n=9) before and after a natural inhalation challenge over 5 hours.
• They evaluated the expression of mRNA of two pro-inflammatory cytokines, namely tumor necrosis factor (TNF)-alpha and interleukin (IL)-1beta, along with two chemokines, IL-8 and macrophage inflammatory protein (MIP)-2.

Results

• After exposure to mouldy hay, horses with heaves exhibited significant airway obstruction and increased numbers of neutrophils in their bronchoalveolar lavage samples, compared to control horses.
• Despite this, there was no difference in the expression of TNF-alpha, IL-1beta, IL-8, and MIP-2 mRNAs between the heaves-affected and control group.

Conclusion

• The findings suggested that the release of cytokines and chemokines by peripheral blood neutrophils may not be necessary for the development of heaves in horses.
• This opens up new possibilities for the understanding and treatment of heaves, as the traditional understanding of the role of neutrophils and their release of cytokines and chemokines in causing inflammation and recruiting other immune cells may need to be re-evaluated.