Neutrophilic airway inflammation in horses with heaves is characterized bya Th2-type cytokine profile

Heaves in horses shares many similarities with human asthma, including lowe r airway inflammation, reversible airway obstruction, and bronchial hyperre sponsiveness. Extrinsic asthma is an allergic response to environmental all ergens and a similar immunologic mechanism may be implicated in heaves. It is now recognized that a Th2 subset of CD4+ lymphocytes is associated with allergic diseases such as atopic asthma. The purpose of this study was to d etermine whether airway inflammation in heaves is associated with a pattern of expression of cytokine suggestive of a Th2 type response. The expressio n of mRNA, encoding interleukin (IL)-4, IL-5, and interferon gamma (IFN-gam ma) was measured in bronchoalveolar cells from seven horses with heaves and five control horses, using fn situ hybridization and radiolabeled equine-s pecific cRNA probes coding for these cytokines. Bronchoalveolar cells of ho rses with heaves had an increased expression of IL-4 (p = 0.01) and IL-5 (p = 0.02) mRNA and a decreased expression of INF-gamma (p = 0.01) compared w ith control horses. Here we show that inflammatory cells in lungs from hors es. with heaves display a Th2-type cytokine profile that is consistent with the hypothesis that heaves is an allergic condition with similarity to hum an asthma.