Background B cells have been shown to play a key role in the pathogenesis of rheumatoid arthritis (RA). Alterations of B cell homeostasis as well as B cell activation markers, such as B-cell activating factor (BAFF) and A Proliferation-Inducing Ligand (APRIL) have been described in RA patients. Up to our knowledge, no data is currently available on differences between treatment naïve patients and those receiving disease modifying anti-rheumatic drugs (DMARDs), regarding B-cell surface expression as well as levels of circulating BAFF/APRIL.
Objectives The aim of this study is to investigate disturbance of B cell as well as B cell activation markers namely BAFF and APRIL in patients with rheumatoid arthritis comparing treatment naive patients with those receiving disease modifying anti-rheumatic drugs.
Methods Sixty RA patients and 30 healthy controls were enrolled. Thirty patients receiving non biologic DMARDs and had not received prior biological treatment and 30 treatment naïve patients. Absolute number of blood CD19 B cells was determined by flow cytometry using the CD19-PE Kit (Immunotech, France). BAFF and APRIL blood concentration was measured using commercially available ELISA kits (Bosterbio, USA).
Results There was statistically significant difference (p-value <0.05) between different study groups as regard B cell count with low mean among treated RA patients (137.2±60.5) and high mean among controls (243.7±22.5). The B cell count was diminished in the two groups of RA patients, however it is more pronounced in treated patients. Circulating BAFF levels were increased in RA compared to HC (p-value <0.05) with more increase in patients on treatment. Circulating APRIL levels were significantly lower (p-value <0.05) in treatment naïve rheumatoid arthritis patients (343.9±21.7) than the control group (371.5±24.3). However, there was no statistical significant difference (p-value >0.05) between each of treated rheumatoid arthritis group and controls or with non treated rheumatoid arthritis group.
Conclusions More decrease in B cell count and more increase in BAFF level were observed in RA patients receiving non-biologic DMARDs. Conversely, APRIL levels were not affected by treatment.
The contribution of B lymphocyte to RA pathogenesis goes beyond autoantibody production. Disturbances in B cell homeostasis in RA are not only due to disease process itself but closely related to the use of anti-rheumatic drugs.
Kotzin BL (2005) The role of B cells in the pathogenesis of rheumatoid arthritis. J Rheumatol Suppl 73: 14–18.
Edwards JC, Cambridge G.(2006) B-cell targeting in rheumatoid arthritis and other autoimmune diseases. Nat Rev Immunol. May;6(5):394–403.
Ng LG, Mackay CR, Mackay F (2005) The BAFF/APRIL system: life beyond B lymphocytes. Mol Immunol 42: 763–772.
Vincent F., Saulep-Easton D., Figgett W., Fairfax K., Mackay F. (2013) The BAFF/APRIL system: emerging functions beyond B cell biology and autoimmunity. Cytokine Growth Factor Rev 24: 203–215.
Disclosure of Interest None declared