title: Immunoglobulin free light chains in adult atopic dermatitis patients do not correlate with disease severity.
abstract: BACKGROUND
  Although total IgE levels have been proposed as a biomarker for disease severity in atopic dermatitis (AD) and are increased in the majority of AD patients, they do not correlate with disease severity during short-term follow-up. During the synthesis of immunoglobulins, free light chains (Ig-FLCs) are produced in excess over heavy chains. In comparison with IgE molecules, Ig-FLCs have a very short serum half-life. Therefore, Ig-FLCs might be more suitable as a biomarker for disease severity during follow-up. Recent studies showed increased serum levels of kappa Ig-FLCs in infants with AD, correlating with disease severity. The aim of this study was to investigate serum kappa Ig-FLC levels in adults with AD, and their correlation to disease severity.
  
  
  METHODS
  Serum kappa If-FLC and total IgE levels were measured in 82 moderate to severe AD patients and 49 non-atopic controls. Blood was collected from patients before start of treatment with potent topical steroids (European classification: III-IV). 32 patients were treated during a clinical admission, and in this subpopulation a second blood sample was taken after 2 weeks of treatment. Clinical severity was determined by the Six Area Six Sign Atopic Dermatitis (SASSAD) severity score and a panel of serum biomarkers, including thymus and activation-regulated chemokine (TARC).
  
  
  RESULTS
  Serum kappa Ig-FLCs levels in adult AD patients were not increased compared to non-atopic controls. Moreover, we observed no correlation between kappa Ig-FLC serum levels and disease severity determined by SASSAD and a panel of serum biomarkers, including TARC. Serum kappa Ig-FLC levels did also not decrease during treatment.
  
  
  CONCLUSIONS
  There are no differences in serum kappa Ig-FLC levels between adult patients suffering from moderate to severe AD compared to non-atopic controls. Moreover, serum levels of kappa Ig-FLCs cannot be used as a biomarker for disease severity in adult AD.
authors.affiliation: Department of Dermatology and Allergology, University Medical Center Utrecht, Heidelberglaan 100, 3584 CX Utrecht, The Netherlands.
authors.forename: J L
authors.initials: JL
authors.lastname: Thijs
authors.affiliation: Nutricia Research, Utrecht, The Netherlands ; Utrecht Institute for Pharmaceutical Sciences, Faculty of Science, Utrecht University, Utrecht, The Netherlands.
authors.forename: K
authors.initials: K
authors.lastname: Knipping
authors.affiliation: Department of Dermatology and Allergology, University Medical Center Utrecht, Heidelberglaan 100, 3584 CX Utrecht, The Netherlands.
authors.forename: C A F
authors.initials: CA
authors.lastname: Bruijnzeel-Koomen
authors.affiliation: Nutricia Research, Utrecht, The Netherlands ; Utrecht Institute for Pharmaceutical Sciences, Faculty of Science, Utrecht University, Utrecht, The Netherlands.
authors.forename: J
authors.initials: J
authors.lastname: Garssen
authors.affiliation: Department of Dermatology and Allergology, University Medical Center Utrecht, Heidelberglaan 100, 3584 CX Utrecht, The Netherlands.
authors.forename: M S
authors.initials: MS
authors.lastname: de Bruin-Weller
authors.affiliation: Department of Dermatology and Allergology, University Medical Center Utrecht, Heidelberglaan 100, 3584 CX Utrecht, The Netherlands.
authors.forename: D J
authors.initials: DJ
authors.lastname: Hijnen
keywords: Atopic dermatitis; Biomarker; Eczema; Free light chains; Serum kappa Ig-FLCs; Total IgE