Expression of toll-like receptor 2 mRNA in bronchial epithelial cells is not induced in RAO-affected horses.
Authors: Berndt A, Derksen F J, Venta P J, Karmaus W, Ewart S, Yuzbasiyan-Gurkan V, Robinson N E
Journal: Equine veterinary journal
Summary
# Editorial Summary: TLR2 Expression and RAO Pathogenesis Recurrent airway obstruction (RAO) involves complex inflammatory mechanisms that extend beyond simple allergic responses, with stable housing triggering clinical signs in susceptible horses. Berndt and colleagues investigated whether bronchial epithelial cells from RAO-affected horses mount a normal innate immune response to fungal antigens by examining toll-like receptor 2 (TLR2) messenger RNA expression—a key pathway through which fungal products normally stimulate airway inflammation and interleukin-8 production in humans. Surprisingly, they found that bronchial epithelial cells from RAO horses failed to upregulate TLR2 mRNA expression in response to stimulation, suggesting a fundamental defect in this innate immune signalling pathway rather than its overactivation. This counterintuitive finding implies that RAO pathophysiology may involve either a compensatory dysregulation of alternative inflammatory pathways or impaired epithelial barrier function that bypasses the need for classical TLR2-mediated responses. For practitioners, this work underscores that RAO is not simply a hypersensitivity condition and suggests that anti-inflammatory management strategies targeting downstream mediators (such as IL-8) rather than blocking initial pattern recognition may prove more effective than approaches assuming standard immune overreactivity.
Read the full abstract on PubMed
Practical Takeaways
- •RAO involves impaired innate immune signaling rather than typical allergic responses, suggesting current treatment approaches may need reconsideration
- •Understanding that TLR2 pathway dysfunction in RAO could inform development of targeted anti-inflammatory therapies beyond standard corticosteroid use
- •Environmental management remains critical since housing conditions trigger RAO despite underlying immune defects in affected horses
Key Findings
- •TLR2 mRNA expression in bronchial epithelial cells is not induced in RAO-affected horses despite fungal product exposure
- •Innate immune pathway involving TLR2 and IL-8 production appears dysregulated in RAO pathophysiology
- •A20 zinc finger protein regulation of TLR2 signaling may be altered in RAO-affected airways