EXTENDED REPORT

Serum immunoglobulin free light chain assessment in rheumatoid arthritis and primary Sjögren’s syndrome

J-E Gottenberg¹, F Aucouturier², J Goetz³, C Sordet⁴, I Jahn³, M Busson², J-M Cayuela⁵, J Sibilia⁴, X Mariette¹

¹ Rhumatologie, Université Paris-Sud 11, INSERM U802, Hôpital Bicêtre, Assistance Publique des Hôpitaux de Paris, Le Kremlin Bicêtre, France
² Immunologie et Histocompatibilité, Hôpital Saint-Louis, AP-HP Paris, France
³ Immunologie, Hôpitaux Universitaires de Strasbourg, Strasbourg, France
⁴ Rhumatologie, Hôpital de Hautepierre, Hôpitaux Universitaires de Strasbourg, Strasbourg, France
⁵ Laboratoire d’Hématologie, INSERM U462, Hôpital Saint-Louis, AP-HP, Paris, France

Correspondence to:
Professor X Mariette
Service de Rhumatologie, Hôpital Bicêtre, 78 rue du Général Leclerc, 94275 Le Kremlin Bicêtre, France;xavier.mariette{at}bct.aphp.fr

Background: B cell activation may result in an increased secretion of immunoglobulin free light chains (FLCs) in autoimmune diseases.

Objective: To analyse serum FLC levels in patients with rheumatoid arthritis and in those with primary Sjögren’s syndrome (pSS).

Patients and methods: Blood samples were collected from 80 healthy blood donors, 50 patients with rheumatoid arthritis and 139 patients with pSS. Serum FLC level was measured using a new quantitative immunoassay.

Results: Mean (standard error (SE)) serum and FLC levels were significantly higher in patients with rheumatoid arthritis and in those with pSS than in controls ( : 18.9 (1.1) and 16.3 (1.4) v 10.5 (0.4) mg/l, p<0.001 and p = 0.001, respectively; : 16.7 (1.2) and 19.3 (1.5) v 11.6 (0.6) mg/l, p<0.001 for both). 18 (36%) patients with rheumatoid arthritis and 31 (22.3%) patients with pSS had abnormal serum FLC levels (increased or levels and abnormal ratio of :). Serum and levels were correlated with other B cell activation markers in both diseases. FLC levels increased with disease activity, because, unlike total gammaglobulin and immunoglobulin G levels, they were significantly correlated with Disease Activity Score 28 in patients with rheumatoid arthritis (p = 0.004 for , p = 0.05 for ) and with extraglandular involvement in pSS (p = 0.01 for , p = 0.04 for ).

Conclusion: FLC levels are increased and correlate with disease activity in patients with rheumatoid arthritis and in those with pSS, two diseases in which increased risk of lymphoma could result from persistent B cell activation and disease activity. Further studies are required to determine whether FLC assessment could represent a relevant biomarker for response to treatment (especially B cell depletion) and for the risk of lymphoma in autoimmune diseases.

Abbreviations: CCP, cyclic citrullinated peptide; DAS, Disease Activity Score; FLC, free light chain; MGUS, monoclonal gammapathy of undetermined significance; pSS, primary Sjögren’s syndrome

CiteULike    Complore    Connotea    Del.icio.us    Digg    Reddit    Technorati    What's this?

This article has been cited by other articles:

• Candon, S, Gottenberg, J E, Bengoufa, D, Chatenoud, L, Mariette, X (2009). Quantitative assessment of antibodies to ribonucleoproteins in primary Sjogren syndrome: correlation with B-cell biomarkers and disease activity. Ann Rheum Dis 68: 1208-1212 [Abstract] [Full Text]  
• Terrier, B, Sene, D, Saadoun, D, Ghillani-Dalbin, P, Thibault, V, Delluc, A, Piette, J-C, Cacoub, P (2009). Serum-free light chain assessment in hepatitis C virus-related lymphoproliferative disorders. Ann Rheum Dis 68: 89-93 [Abstract] [Full Text]