Transbronchial Brush (TBBr) detection of activated T Cells identifies patients at risk of progressive Bronchiolitis Obliterans Syndrome (BOS)

Purpose Lymphocytic bronchiolitis (LB) is one of the strongest risk factors for subsequent BOS, but the operating characteristics of transbronchial biopsy (TBBx) for LB diagnosis are poor. We hypothesised that combining transbronchial brush (TBBr) with flow cytometric phenotyping of epithelial lymphocyte populations would better assess allograft health. Methods and Materials TBBr and bronchial brushings were performed to obtain small and large airway epithelium respectively at surveillance and diagnostic bronchoscopy. Cells were stained with cytokeratin, CD3, CD8, CD103 (intraepithelial T cells) and granzyme B (GrB) before flow cytometry was performed. Data are presented as median (interquartile range) percentage of total cells. Results 67 patients (23 CF, 21 COPD, 13 IPF, 91% bilateral, median age 49.7 yrs, 51% male, median 14.3 (3.9-49.5) months post-transplant) were assessed. Bronchial CD3 + (p=0.006), CD8 + (p=0.044), CD3 + CD103 + (p=0.022) and CD3 + GrB + (p=0.009) cells were increased in those undergoing diagnostic bronchoscopy (n=23) and those with A grade rejection (n=5 A1, n=3 A2, n=1 A3) compared to those having a surveillance bronchoscopy (n=35). In contrast, only the CD3 + GrB + subset was increased in the bronchiolar region (1.44 (0.9-3.0) vs 0.73 (0.4-1.5), p=0.005). There was no correlation between any subset and immunosuppressant dose or level, however treatment of A grade rejection with augmented immunosuppression led to a reduction in the bronchial CD3 + (p=0.043) and bronchiolar CD3 + GrB + (p=0.012) subsets. Only the bronchiolar CD3 + GrB + fraction was increased (1.92 (1.0-4.1) vs 1.0 (0.4-1.7), p=0.028) in the 18% of the cohort who experienced progressive BOS in the following 13.3 (5.8-18.3) months. TBBx did not predict outcome. Conclusions Infiltration of the bronchiolar region by activated CD3 + GrB + T cells is associated with subsequent allograft dysfunction. As this subset is responsive to augmented immunosuppression, vigilant immune monitoring using TBBr could prevent BOS.