Surfactant Protein D and KL-6 as Serum Biomarkers of Interstitial Lung Disease in Patients with Scleroderma

Abstract

Serum levels of SP-D and KL-6 appear to be indicative of "alveolitis" in SSc patients as defined by the SLS, and are significantly higher than in SSc patients without "alveolitis." Serum SP-D and KL-6 may serve as noninvasive serological means of assessing interstitial lung disease in patients with SSc.

Serum biomarkers in idiopathic pulmonary fibrosis

“…Upon epithelial breakdown, KL-6 is thought to leak into the circulation, where it can be measured by a commercially available ELISA kit. KL-6 has been studied extensively in mainly Japanese patients, where serum levels were found to be increased in various interstitial lung diseases such as radiation pneumonitis [22][23][24], CTD-associated lung disease [25][26][27] and drug induced pneumonitis [28]. Interestingly, KL-6 may have a role in fibrosis itself, as it was shown to induce proliferation of lung fibroblasts in vitro [29].…”

The Ambitious Goal of Validating Prognostic Biomarkers for Systemic Sclerosis-related Interstitial Lung Disease

“…With regard to SP-D, a lipoprotein secreted by type II alveolar epithelial cells and airway Clara cells, together with SP-A, this pneumoprotein is involved in the maintenance of alveolar surface tension and the host defense system in the lung, and has been found to be elevated in patients with SSc-ILD, correlating with degree of fibrosis and pulmonary function test results 6,20 . Elhaj, et al found no difference in the predictive quality of baseline or longitudinal SP-D in serum compared to CCL18 separately as well as combined in a score.…”

“…The Scleroderma Lung Study (SLS) and the Genetics versus Environment in Scleroderma Outcome Study (GENISOS) assembled the largest cohorts for this purpose 6,7 . These efforts were intended mainly to drive treatment choice, but also to avoid serial HRCT scans for patient followup to reduce radiation exposure.…”

Surfactant Protein D Family: Potential for Diagnosis or Monitoring Therapy in Autoimmune Diseases?

“…Closer to home in rheumatology, patients with scleroderma and alveolitis had higher SP-D levels than scleroderma patients free of lung involvement, although other markers such as KL-6 were considered more strongly predictive of disease progression 2,9,10 .…”