Phagocytosis, bacterial killing, and cytokine activation of circulating blood neutrophils in horses with severe equine asthma and control horses.

This research study explores phagocytosis, bacterial killing, and cytokine activation of circulating blood neutrophils in horses with severe equine asthma and healthy horses. It examines whether neutrophils in asthmatic horses have increased activation of proinflammatory cytokines and chemokines, and decreased activation of anti-inflammatory cytokines in response to bacteria.

Objective

• The objective this study is to analyze the in vitro phagocytosis and bacteria-killing activity of circulating blood neutrophils in horses with severe equine asthma. It also seeks to determine if these neutrophils in asthmatic horses have an increased expression of proinflammatory cytokines TNF-α and IL-8 and a decreased expression of anti-inflammatory cytokine IL-10 when exposed to bacteria.

Animals and Procedures

• The study used 6 horses with severe equine asthma and 6 healthy horses as controls.
• Circulating blood neutrophils were isolated from both the asthmatic and control horses.
• Phagocytosis was evaluated using flow cytometry, a technique used to measure cell components.
• The bacteria-killing ability of the neutrophils was assessed using Streptococcus equi and Streptococcus zooepidemicus as target bacteria. The responsiveness of cytokine mRNA in these neutrophils was assessed through a quantitative PCR assay.

Results

• Neutrophils from horses with severe equine asthma showed a significantly lower ability to kill S. zooepidemicus compared to the control horses. However, this was not the case with S. equi.
• There were no significant differences in phagocytosis and mRNA expression of TNF-α, IL-8, and IL-10 between the two groups of horses.

Conclusions and Clinical Relevance

• The study concludes that horses with severe equine asthma have impaired bactericidal activity of their circulating blood neutrophils. This could potentially lead to an increased susceptibility to infections.