KL-6 Concentrations Research Articles

Serum KL‐6 levels in pediatric patients: Reference values for children and levels in pneumonia, asthma, and measles patients

Serum KL-6 reflects alveolar damage and regeneration of type II pneumocytes, indicating disease activity in various interstitial lung diseases. We conducted a descriptive and observational multiple case-control study to determine the distribution of serum KL-6 levels in pediatric patients with or without respiratory diseases. Subjects were recruited from the patients of a teaching hospital in the suburb of Tokyo. A consecutive series of 401 children (0-16 years old) underwent blood sampling for many clinical reasons. They comprised the following four groups: pneumonia (n = 96), bronchial asthma (n = 101), measles (n = 102), and nonrespiratory diseases (n = 102) as a control group. Standard upper limits of serum KL-6 in a group of children with nonrespiratory disease were 250 U/mL, or half the adult level. No gender or age differences were observed. Elevated serum KL-6 concentrations were observed in severe pneumonia, acute exacerbations of asthma, and measles pneumonia. In the measles group, KL-6 values reflected the presence and severity of complicating pneumonia. We conclude that serum KL-6 levels exceeding 250 U/mL were rarely observed in children without respiratory diseases. In contrast, a substantial proportion of children with common respiratory diseases showed mild to moderate increases in serum KL-6 levels. Elevated serum KL-6 in these children may reflect the presence of alveolar damage, followed by regeneration of type II pneumocytes. However, in order to use serum KL-6 as a marker of interstitial lung diseases in children, a cutoff level should be determined separately.

Serum KL-6 Levels in Patients With Pulmonary Complications After Allogeneic Bone Marrow Transplantation

KL-6, a mucinous high-molecular weight glycoprotein expressed on type 2 pneumocytes, has been shown to be elevated in the serum and bronchoalveolar lavage fluid of patients with interstitial pneumonitis (IP). We measured the serum levels of KL-6 in patients after they had undergone allogeneic bone marrow transplantation (BMT) to determine whether KL-6 could be a clinically useful indicator for the development of IP. The serum concentrations of KL-6 were determined by a sandwich-type enzyme-linked immunosorbent assay using an anti-KL-6 monoclonal antibody. A total of 1028 samples were tested from 76 patients (78 transplantations) who received BMTs. The KL-6 values were markedly elevated in patients with pulmonary complications, but not in those with acute and chronic graft-versus-host disease, hemorrhagic cystitis, herpes encephalitis, sepsis, and veno-occlusive disease. The serum levels of KL-6 from patients with pulmonary complications were significantly higher than from those without pulmonary complications (P < .001) and those with other complications (P < .001). Of the 12 patients with pulmonary complications, 6 had idiopathic IP (IIP). The levels were not high at the onset of IIP. Four of 6 IIP patients showed marked elevations of KL-6 levels in parallel with the severity of IP and died of respiratory failure without response to treatment. Assessment of serum KL-6 levels might not be useful for the early diagnosis of IP, but may be a useful indicator for monitoring the severity of IP after BMT.

KL-6 as a novel marker for activities of interstitial pneumonia in connective tissue diseases.

The objective of this study was to determine the role of serum KL-6 levels as a marker for the activity of interstitial pneumonia in patients with connective tissue diseases. The serum concentrations of KL-6, a glycoprotein produced mainly by pulmonary type II epithelial cells, were measured in 21 patients with connective tissue disease. The activity of interstitial pneumonia was compared with the associated serum KL-6 concentrations. Serum KL-6 concentrations in patients with interstitial pneumonia were significantly higher than those in the controls. Among patients with active interstitial pneumonia, serum KL-6 concentrations following the treatment (after improvement) were significantly lower than the pretreatment values. The extent of the pulmonary fibrosis correlated positively with the serum KL-6 concentrations during the inactive phase of the interstitial pneumonia. These results suggest that sequential measurement of serum KL-6 levels is a new and useful means for the evaluation of interstitial pneumonia in patients with connective tissue diseases.