Histamine bronchoprovocation does not affect bronchoalveolar lavage fluid cytology, gene expression and protein concentrations of IL-4, IL-8 and IFN-γ

In diagnosing inflammatory airway disease (IAD) in performance horses, a histamine bronchoprovocation (HBP) test is often performed. In previously published studies, HBP is usually undertaken prior to cytological examination of the bronchoalveolar lavage (BAL) cells. The purpose of this study was to determine if HBP alters (1) the total nucleated cell numbers and distribution in BAL fluid (BALF) and (2) the mRNA and protein concentrations of selected cytokines in BAL cells and BALF, respectively. BALF was initially collected endoscopically from the right middle or diaphragmatic lung lobe in eight healthy young Standardbred horses. Five to six days later, HBP was performed by aerosolization of histamine (8 mg) over a 2 min period. BALF was again collected within 2–4 h of the HBP from the left middle or diaphragmatic lung lobe. In both samples, total and differential WBC counts were obtained. The gene expressions of interleukin-4 (IL-4), IL-8, interferon-γ (IFN-γ) and β-actin in BAL cells were measured using real-time RT-PCR. The cytokine protein concentrations were measured in the BALF using ELISA. HBP was not associated with either a change in the total BAL cell number or in the distribution of the BAL cells. BAL cell expression of IL-4, IL-8 and IFN-γ, detected in all samples with the exception of IL-4 in one horse (post-HBP), was not altered as a result of HBP. HBP was not associated with a significant change in IL-8 or IFN-γ concentrations in the BALF. IL-4 protein was undetectable in BALF either prior to or following HBP. We conclude that HBP can precede BALF collection performed within 2–4 h of the former without affecting selected parameters analysed in the BAL cells or BALF.