Single-cell transcriptomics delineates the immune cell landscape in equine lower airways and reveals upregulation of FKBP5 in horses with asthma

Equine asthma (EA) is a heterogenous, complex disease, with a significant negative impact on horse welfare and performance. EA and human asthma have fundamental similarities, making EA a useful large animal disease model. Bronchoalveolar lavage fluid (BALF) provides a snapshot sample of the immune cells occupying the alveolar space and is one of the most relevant sample types for studies of chronic inflammation in the lung. In this study, we performed single cell RNA-seq analysis of equine BALF cells in order to study the immune cell landscape of the respiratory tract of horses diagnosed with mild-to-moderate EA (mEA) and healthy controls. We characterized the major immune cell populations in equine BALF, as well as subtypes thereof. Interestingly, the most significantly upregulated gene found in mEA was FKBP5, a chaperone protein involved in regulating the assembly, activity, and sensitivity of the glucocorticoid receptor.