Serum KL-6 concentrations are associated with molecular sizes and efflux behavior of KL-6/MUC1 in healthy subjects.

Background: Serum KL-6, a sialylated sugar chain on human MUC1, is used as a marker of interstitial lung diseases. We recently reported that efflux behavior of KL-6/MUC1 from the alveoli into the bloodstream assessed by molecular analysis differed according to genetically determined molecular sizes and influenced serum KL-6 concentrations in sarcoidosis. This study was designed to investigate associations between molecular size and efflux behavior of KL-6/MUC1, and factors contributing to serum KL-6 concentrations in healthy subjects.

Methods: Western blot analysis using anti-KL-6 antibody was performed on serum obtained from 250 healthy subjects.

Results: The efflux behavior of KL-6/MUC1 differed according to the genetically determined molecular sizes in healthy subjects. In subjects having low molecular size, there were significant associations between smoking status, aging, renal function and serum KL-6 concentrations. However, these associations were not significant in the subjects having higher molecular size and the efflux behavior of high molecular size was the only significant determinant of serum KL-6 concentrations.

Conclusions: This study showed an association between KL-6/MUC1 efflux based on molecular size and serum KL-6 concentrations in healthy subjects. We propose that the molecular size and efflux behavior of KL-6/MUC1 should be considered when interpreting serum KL-6 concentrations.