Soluble CD26 is inversely Associated with Disease Severity in Patients with Chronic Eosinophilic Pneumonia

Backgrounds: CD26, a multifunctional T cell surface glycoprotein, is a type II transmembrane protein containing only six amino acid residues in its cytoplasmic region. In addition to its membrane form, CD26 exists in plasma in a soluble form (sCD26), which is thought to be the extracellular domain of the molecule cleaved from the cell surface. Recent studies indicated CD26 have an important role in the pathogenesis of asthma, known as Th2 like disease. The function of CD26 in the esosinophlic lung disease is not well understood. Methods: Serum sCD26 was determined by enzyme-linked immunosorbent assay in patients with acute eosinophilic pneumonia, chronic eosinophilic pneumonia (CEP), and sarcoidosis, and in healthy volunteers, to establish its value for discriminating between disease entities and as marker of disease activity. Results: Soluble CD26 was significantly reduced in CEP and was related to disease severity. In particular, sCD26 was inversely correlated with arterial oxygen tension in CEP. Conclusion: Serum levels of sCD26 might appear to be useful as a new marker of CEP disease activity.