341: Explaining the Bronchiolitis Obliterans Syndrome (BOS) Phenotype – Epithelial-Mesenchymal Transition (EMT) Occurs More Readily in Small Airway Epithelium

BOS Is Associated With Increased Cytotoxic Proinflammatory CD8 T, NKT-Like, and NK Cells in the Small Airways

BACKGROUND

Immunosuppression therapy after lung transplantation fails to prevent bronchiolitis obliterans syndrome (BOS) in many patients, primarily a disease of the small airways. We have reported that BOS is associated with a lack of suppression of cytotoxic mediators, and proinflammatory cytokines, in peripheral blood T, NKT-like (particularly CD8+) and NK cells. We also showed a loss of glucocorticoid receptor (GCR) in proinflammatory lymphocytes after transplant. It is unknown whether these proinflammatory lymphocytes target the small and/or large airways in BOS.

METHODS

Blood, bronchoalveolar lavage, large proximal, and small distal airway brushings were collected from patients with BOS (n = 10), stable lung transplant patients (n = 18), and healthy aged-matched controls (n = 10). Intracellular cytotoxic mediators (perforin/granzyme B), proinflammatory cytokines (IFNγ/TNFα), and expression of GCR were determined in lymphocytes subsets from cultured blood using flow cytometry.

RESULTS

Increases in CD8 T cells, NKT-like cells, and NK cells were found in the small distal airways in BOS compared with stable patients and controls. An increase in perforin, granzyme B, IFNγ, TNFα, and a loss of GCR from these lymphocyte subsets was also found in BOS. GCR expression by CD8+ T cells from small airways correlated with FEV1 (R = 0.834, P = 0.039). Many of these changes significantly differed from those in the large airways.

CONCLUSIONS

BOS is associated with increased cytotoxic/proinflammatory CD8+ T, NKT-like, and NK cells in the small airways. Treatments that increase GCR in these lymphocyte subsets may improve graft survival.