Objective—To examine effects of in vitro exposure to solutions of hay dust, lipopolysaccharide (LPS), or β-glucan on cytokine expression in pulmonary mononuclear cells isolated from healthy horses and horses with recurrent airway obstruction (RAO).
Animals—8 RAO-affected and 7 control horses (experiment 1) and 6 of the RAO-affected and 5 of the control horses (experiment 2).
Procedures—Bronchoalveolar lavage cells were isolated from horses that had been stabled and fed dusty hay for 14 days. Pulmonary mononuclear cells were incubated for 24 (experiment 1) or 6 (experiment 2) hours with PBS solution or solutions of hay dust, β-glucan, or LPS. Gene expression of interleukin (IL)-17, IL-23(p19 and p40 subunits), IL-8, IL-1β, and chemokine (C-X-C motif) ligand 2 (CXCL2) was measured with a kinetic PCR assay.
Results—Treatment with the highest concentration of hay dust solution for 6 or 24 hours increased expression of IL-23(p19 and p40), IL-8, and IL-1β in cells from both groups of horses and increased early expression of IL-17 and CXCL2 in RAO-affected horses. Lipopolysaccharide upregulated early expression of IL-23(p40) and IL-8 in cells from both groups of horses but only late expression of these cytokines in cells from RAO-affected horses. Treatment with β-glucan failed to increase cytokine expression at 6 or 24 hours.
Conclusions and Clinical Relevance—Cells from RAO-affected horses were not more responsive to the ligands tested than were cells from control horses, which suggests a minimal role of mononuclear cells in propagation of airway neutrophilia in horses with chronic RAO.