Hakata antigen, a new member of the ficolin opsonin p35 family, is a novelhuman lectin secreted into bronchus alveolus and bile

Hakata antigen was first reported as a serum protein that reacted with an a utoantibody from patients with systemic lupus erythematosus. Recently, it h as been found that Hakata antigen is a new member of the ficolin/opsonin p3 5 family, which is a distinct lectin family, on the basis of homology of st ructures and the common characteristic of possessing lectin activity. In th is study we analyzed the tissue distribution of Hakata antigen. Hakata anti gen mRNA and protein were generated in the lung and liver. In the lung, Hak ata antigen was produced by both ciliated bronchial epithelial cells and Ty pe II alveolar epithelial cells and was secreted into the bronchus and alve olus. In the liver, Hakata antigen was produced by bile duct epithelial cel ls and hepatocytes and was also secreted into the bile duct. These results demonstrate that Hakata antigen is a unique lectin protein that exists not only in serum but also in bronchus/alveolus and bile, and indicate that Hak ata antigen plays a role in bronchus/alveolus and bile under physiological conditions.