The lung injury such as interstitial pneumonia and pulmonary fibrosis causes severe respiratory failure resulting in poor prognosis. Recently, SP-A and SP-D as well as KL-6 are known as serum markers for these lung injuries. SP-A and SP-D are the surfactant specific proteins and synthesized by alveolar type II epithelial cells. KL-6 is one of the membrane proteins of type II cells. As these proteins are highly specific to the lungs, they are used as serum markers for diagnosis, determination of the severity, follow up of the clinical course and prognosis of interstitial pneumonia. Although these markers are clinically useful, further information on the mechanisms why they are present in the serum and also on the relationships between these proteins needs to be accumulated.

*Department of Laboratory Medicine, School of Medicine, Iwate Medical University, Morioka 020-8505