Abstract 1667: Increased Serum BAFF Levels in Patients with Inflammatory Myopathies
Authors:
Olga Krystufkova1, Therese Vallerskog2, Sevim B. Helmers2, Herman Mann1, Ivana Putova1, Vivianne Malmstrom2, Christina Trollmo2, Jiri Vencovsky1, Ingrid E. Lundberg2.
1Institute of Rheumatology, Prague, Czech Republic; 2Rheumatology Unit, Department of Medicine, Karolinska University Hospital, Solna,Karolinska Institute, Stockholm, Sweden
Background:
Autoantibodies are frequently present in patients with idiopathic inflammatory myopathies. The mechanisms for autoantibody production and significance of B cells in myositis remain poorly understood. The cytokine BAFF (B-cell activating factor of the TNF family, also known as BLyS) is crucial for B-cell maturation and
survival and is believed to play a role in autoantibody production.
Purpose:
To investigate serum levels of BAFF in patients with myositis and correlate these to clinical phenotype, autoantibody profile and treatment.
Methods:
BAFF levels in sera from 50 patients with dermatomyositis (DM), 44 with polymyositis (PM), 6 with inclusion body myositis (IBM) and 30 matched controls were measured by ELISA. Autoantibodies to Jo-1 (39/100), Mi-2 (9/72), PM-Scl (11/72) and Ro52 (4/100) were detected by line-blot assay. Serum levels of CRP and creatine phosphokinase (CPK) were available from 82 and 87 patients respectively. Median disease duration was 3 years; 25 patients were considered early cases .82/100 patients were treated with glucocorticoids, 52 with DMARDs and 13 had no treatment. Patients were classified as having low (n=54), moderate (n=37) or high (n=9) disease activity.
Results:
Serum BAFF levels were elevated in patients (median 1.12 ng/ml) compared to healthy controls (0.85 ng/ml; p<0.005) and in patients with DM (1.28 ng/ml) compared to PM (0.88 ng/ml; p<0.05) and to controls (p<0.001). Patients with interstitial lung disease (ILD n=43) displayed higher median levels of BAFF (1.29 ng/ml) compared to controls (p<0.01). Patients with anti-Jo-1, but not those with anti-Mi-2, anti-PM-Scl or anti-Ro52 autoantibodies, had significantly higher median levels of BAFF (1.42 ng/ml) compared to controls (p<0.001). Patients with high disease activity had higher serum BAFF levels (3.3 ng/ml) compared to those with moderate and low activity (1.09 and 1.1ng/ml; p<0.05). Patients with serum levels of BAFF higher than 2 SD above the mean of control samples had increased CPK but not CRP levels. Serum BAFF and CPK levels displayed a weak positive correlation (rs=0.37; p<0.001). A negative correlation was recorded between serum levels of BAFF and cumulative glucocorticoid doses in early
myositis cases (rs=-0.65; p<0.001).
Conclusion:
Myositis patients demonstrate elevated serum levels of BAFF, particularly those with DM, ILD, anti-Jo-1 antibodies or high disease activity. These observations, in combination with the correlation between levels of BAFF and CPK and a negative correlation with cumulative dose of glucocorticoids in early cases indicate that BAFF could have a role in the pathogenesis of myositis.
Editorial Comment:
The role of BAFF (BlyS) has been explored in other rheumatic diseases such as SLE. BAFF could have a role in the pathogenesis of myositis and, most importantly, may be a therapeutic target.
