(276) - Elevated Hyaluronan Is Associated with Bronchiolitis Obliterans Syndrome

Abstract

s S107 and bronchiolitis obliterans syndrome (BOS), of which the exact pathophysiology remain elusive. A previous study demonstrated that increased bronchoalveolar lavage eosinophilia predisposed to CLAD. We further investigated the presence of eosinophils in explants lung tissue of CLAD. Methods: Sections of BOS (n= 16) and RAS (n= 16) lungs were stained and quantified compared to (non-transplant) control lungs (n= 20). Eosinophils, identified by the marker EG2, were counted in three different compartments; around the airway, in the parenchyma and around the blood vessel. Results were represented as the mean number (±SEM) of cells per high power field. Results: Representative staining of BOS (A), RAS (B) and control (C) are provided in figure 1. Around the airways, eosinophils were significantly increased in BOS (16.7±4.8; p< 0.05) and in RAS (13.4±4.0; p< 0.05) compared to control (2.8±0.8). In the parenchyma, there were more eosinophils present in BOS (8.8±1.4; p< 0.05), but not in RAS (8.2±2.2), compared to control (3.9±0.9). Around the blood vessels, both BOS (11.4±2.1; p< 0.01) and RAS (9.8±1.9; p< 0.05) demonstrated an increased number of eosinophils compared to control (4.0±0.6). The number of eosinophils around the airways correlated with eosinophil numbers in the parenchyma (R= 0.55, p< 0.0001) and around the blood vessels (R= 0.79, p< 0.0001). Conclusion: Eosinophils, regulated by a Th2 immune response, are increased in BOS and RAS which may implicate a new pathway. These findings may lead to additional therapeutic options to improve outcome after LTx in the future.