Introduction:

Systemic Lupus Erythematosus (SLE) is an autoimmune disease characterized by autoantibodies against nuclear components. The pathogenesis of SLE is poorly understood and disease-specific symptoms or clinical parameters are lacking. Since increased levels of cell-free DNA (cf-DNA) are detected in SLE patients compared with healthy individuals cf-DNA is discussed as potential marker for SLE. The aim of this study was to determine the levels of cf-DNA in SLE patients compared to healthy controls and to assess fluctuations in cf-DNA concentrations compared to the course of disease progression under standard treatment.

Methods:

35 SLE patients and an equal number of age-matched healthy controls were examined. Additionally, venous blood plasma samples from 27 SLE patients, taken in an interval of 1 to 6 months, were analyzed. Patients were characterized by clinical parameters (e.g. autoantibodies, C3, C4, CRP), SLE disease activity index (SLEDAI) and therapy. Nuclear DNA concentrations in blood plasma were measured by quantitative real-time PCR (qPCR).

Results:

We found that cf-DNA concentrations are significantly higher in SLE patients compared to healthy individuals. There was no clear relationship between cf-DNA and individual clinical parameters. However, fluctuations of cf-DNA levels assessed in serial samples correlated with the medical evaluation of disease status in SLE patients.

Conclusion:

Our results implicate cf-DNA as an individual marker for disease progression. The lack of correlation with clinical parameters might be in part explained by the heterogeneous pathology of SLE. The validity of cf-DNA as additional clinical parameter for disease progression has to be evaluated in further studies.