Increased soluble CD14 in bronchoalveolar lavage fluid of stable lung transplant recipients

Macrophages, neutrophils and infection have been implicated in the genesis of the bronchiolitis obliterans syndrome (BOS) post lung transplantation. sCD14 is a soluble form of a shed-cell surface protein. It is capable of promoting cytokine-induced inflammation and it's presence in clinically stable lung transplant recipients (LTR) might be important as an early marker of BOS. Bronchalveolar lavage (BAL) and blood samples were taken from 26 stable LTR, at or near their best forced expiratory volume in one second who were free from infection. sCD14 levels were measured via enzyme-linked immunosorbent assay. Cell counts were performed on unfiltered BAL. LTR neutrophil count, BAL sCD14 and serum sCD14 levels were higher than controls (median 3.8% versus 1.3%, p<0.05; 11.5 ng·mL-1 versus 6 ng·mL-1, p<0.001; 6.2 μg·mL-1 versus 2.4 μg·mL-1, p<0.05, respectively). BAL albumin and sCD14 correlated (regression coefficient: 0.77, p<0.001). In this hypothesis-generating, cross-sectional study, the authors have described for the first time soluble CD14 levels in the bronchoalveolar lavage and serum of stable lung transplant recipients, and show that these are elevated compared to controls. This is a practicable candidate marker system, which can be tested for a predictive role in bronchiolitis obliterans syndrome following lung transplantation. The origin of this cellular protein and its temporal relationship to the development of the bronchiolitis obliterans syndrome remains to be elucidated in more definitive longitudinal studies, which should include other measurements potentially relevant to the innate immune system, such as bronchoalveolar lavage endotoxin levels.