Tu189 - Bronchoalveolar and Airway Mucosal T Cell Phenotypes and Repertoires Are Distinct in Health and Allergic Asthma

Abstract Text: Asthma affects ~8.7% of individuals in the United States and most commonly is associated with Type 2 inflammation. T cells, specifically T helper type 2 (Th2) cells, drive allergic asthma. Previous studies have examined T cells from the lungs of asthmatics captured via bronchoalveolar lavage (BAL), endobronchial brushings or biopsies. However, whether these different approaches are capturing the same T cell phenotypes and/or clonotypes is unknown. To evaluate this, single-cell RNA sequencing was performed on CD3+ T cells isolated from paired BAL and endobronchial brushings in 3 healthy controls (HC) and 3 allergic asthmatics (AA). T cell receptor (TCR) sequences were recovered using TRUST4 software. Unbiased clustering allowed us to define 6 CD4 and 7 CD8 T cell subsets. Interestingly, Th2 cells were enriched in AA compared to HC when comparing endobronchial brush samples (OR=26.2, P=0.002), but not when examining BAL (OR=1.7, P=0.46), indicating differences in the T cells isolated from the BAL and airway mucosa. In further support of this concept, an up-regulation of resident-memory T cell genes (i.e. ITGAE, CD69) was observed broadly in the cells from endobronchial brushes compared to BAL across T cell types of both lineages. Lastly, TCR repertoire analysis from AA and HC revealed expanded clones with Th1 and cytotoxic CD8 T cells phenotypes found exclusively in the airway mucosa. These results demonstrate that T cell phenotypes and clonotypes are distinct in bronchoalveolar and airway mucosa compartments and sampling the airway mucosa is critical to define T cell biology in diseases such as asthma.