Do Balf Cytokine Profiles Vary Depending on the Sampled Lung in Horses with Unilateral IAD‐Consistent Cytology?

Abstract

Reasons for performing study Little data on BALF cytokine profiles are available from racehorses with IAD; cytological diagnosis being most frequently made from one lung only per horse. Objectives To compare cytokine mRNA expressions and protein concentrations in BALF from both lungs of horses with unilateral IAD‐consistent cytology. Study design Cross‐sectional study. Methods As part of a larger study, 250 ml saline was randomly instilled in one lung and 500 ml in the contralateral lung of 30 clinically healthy Standardbred racehorses. This procedure was repeated 72 h later, inversing the volume per lung. Cytological cut‐off values for IAD diagnosis was neutrophil proportions >10% when instilling 250 ml. For these samples, mRNA expression and concentrations of IL‐1β, IL‐4, IL‐8, IL‐10, IL‐17, TNF‐α and IFN‐γ were determined by RT‐qPCR and ELISA. Results Eleven horses had BALF with IAD‐ and CTL‐consistent cytology from, respectively, each lung, and were enrolled in the study (22 samples). Data were not significantly influenced by the sampling day, and BALF total cell counts or cytokine concentrations were not significantly different among lungs. Relative mRNA expression of IL‐1β (3.887 ± 3.082; P = 0.01) and IL‐10 (3.225 ± 1.710; P = 0.005) were significantly higher in BALF of IAD‐ compared to CTL consistent lungs (respectively 1.408 ± 1.118 and 1.488 ± 1.393); and also correlated to neutrophil proportions (respectively r = 0.54; P = 0.01 and r = 0.65; P = 0.001). Conclusions Differences in cytokine mRNA expression were associated with IAD‐ or CTL consistent BALF cytology in the same racehorses in training. These findings suggest that specific local immune reactions or regulation within the lower airways should be considered in IAD. Ethical animal research: The study was approved by the Regional Animal Ethic Committee, and informed consent was provided by all horse owners. Sources of funding: LABÉO, CISCO‐Oniris and AVEF (French Association of Equine Practitioners). Competing interests: None declared.