Free light chains of immunoglobulins in serum as biomarker of activity in systemic lupus erythematosus


Authors: Hrnčíř Zb;  M. Drahošová 1;  T. Soukup;  J. Tomš
Authors‘ workplace: II. interní klinika a 1Ústav klinické imunologie a alergologie, Lékařská fakulta UK a Fakultní nemocnice, Hradec Králové
Published in: Čes. Revmatol., 21, 2013, No. 1, p. 4-10.
Category: Original Papers

Overview

Background:
The molecules of immunoglobulins (Ig) include two identical heavy and two identical light chains. More light than heavy chains of Ig are produced under physiological conditions, and so free light chains (FLC) may be detected in biological fluids, especially in serum. Systemic lupus erythematosus (SLE) in associated with polyclonal activation of B cells, and propotional elevation of FLC kappa and FLC lambda values in serum with normal relation of FLC kappa:FLC lambda should be expected in active form of SLE.

Objective:
To explore the changes of serum concentration of FLC kappa and FLC lambda as putative biomarkers of SLE disease activity in a prospective, comparative, and cross-over study.

Methods:
Eighty-three adult SLE (ACR/1982, update in 1997) patients and 33 age- and sex-matched healthy controls were enrolled; concomitant infection, monoclonal gammopathy and renal failure in patients under study were excluded. Disease activity was assessed using the Systemic Lupus Erythematosus Disease Activity Index 2000 (SLEDAI-2K): a score ≥6 was considered clinically important. FLC kappa and FLC lambda in serum were analysed by quantitative nephelometric assay and compared against SLEDAI-2K and serological biomarkers IgG, C3, C4, „total“ ANA, anti-dsDNA, and antinucleosome Abs. Statistical analysis using Medcalc-Statistical software programme was made.

Results:
Serum concentration of FLC kappa, FLC lambda and total FLC kappa + FLC lambda in 22 SLE with SLEDAI-2K ≥6, and also in 61 SLE with SLEDAI-2K <6 was significantly higher against healthy controls (p = 0.003 - <0.001) except FLC lambda in SLE with SLEDAI-2K <6 against controls (p > 0.05). In SLE with SLEDAI-2K ≥6 the concentration of FLC kappa, FLC lambda and FLC kappa + FLC lambda was always significantly higher than in SLE with SLEDAI-2K <6 (p < 0.001). In total group of 83 SLE a significant correlation (p < 0.001) was found between SLEDAI-2K score and FLC kappa (r = 0.56), FLC lambda (r = 0.58) and FLC kappa + FLC lambda (r = 0.62). FLC analysis against serum values of Abs under study demonstrated a strong correlation namely between FLC kappa, FLC lambda and FLC kappa + FLC lambda,and antinucleosome Abs (r = 0.59, r = 0.53, and r = 0.59).

Conclusions:
FLC (kappa, lambda and total) concentration in serum correlate strongly with disease activity in SLE and is significantly higher in patients with clinically important SLEDAI-2K ≥6; these results are suggesting that serum FLC may be used as biomarker of SLE disease activity.

Key words:
Free light chains of immunoglobulins, systemic lupus erythematosus, SLEDAI-2K scoring system, biomarkers of disease activity in serum


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Labels
Dermatology & STDs Paediatric rheumatology Rheumatology
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