Cytokine mRNA expression in the bronchoalveolar lavage cells from horses affected by different equine asthma subtypes.

The researchers conducted a study on horses to identify the role of different immune responses and indicators in horses affected by equine asthma (EA). By correlating cytokine mRNA expression levels in bronchoalveolar lavage fluid (BALF) with observable symptoms and lung function, the study found that different types of EA are linked with different immune responses.

Objective and Methodology

• The objective of this study was to analyze the relationship between cytokine mRNA expression in the BALF of horses, various EA subtypes, and lung functions.
• They examined 15 horses, which included physical examinations, airway endoscopies, BALF cytology, and lung function testing. Of these, one horse showed no signs of EA and was used as a healthy control.
• The team used residual BALF cells to check the gene expression levels of various cytokines, namely IL-1β, IL-2, IFN-γ, IL-4, and IL-17A, via quantitative reverse transcription polymerase chain reaction (RT-PCR).
• Finally, the researchers compared cytokine expression between groups and scrutinized the correlation of these indicators with BALF leukocyte counts and lung functionality.

Findings

• The level of IL-1β was found to be positively correlated with the neutrophil (a type of white blood cell) count in the BALF, along with increased respiratory resistance.
• IFN-γ was positively correlated with BALF mast cell count (another type of immune cell).
• IL-4 was more expressed in horses suffering from mixed granulocytic EA than those with neutrophilic EA, correlating positively with mast cells in BALF but inversely with overall breath efficiency and expiratory reactance.
• Interestingly, there was an inverse correlation noted between IL-17A and expiratory reactance.
• The scientists concluded from these results that different immune responses are involved in EA pathogenesis, specifically referring to innate, Th2, and Th17 responses. Out of these, innate immunity was associated with neutrophilic inflammation, and a Th2 response correlated with an increased count of mast cells.

Implications

• This study provides valuable insights into the immunological basis of equine asthma and how different subtypes of the condition might be characterized and potentially treated based on their distinct cytokine production profiles.
• However, the paper mentions that the role of a Th1 response in equine asthma still needs to be clarified.