Background Our laboratory has previously characterized defects in humoral B cell responses of aged mice and humans. These defects include: the reduction in activation-induced cytidine deaminase (AID), required for the generation of optimal antibody responses, and the reduction in the percentage/number of the subset of switched memory B cells (1). AID and switched memory B cells have been proposed to be effective predictive biomarkers of vaccine responses (2). Moreover, we have shown that aging is characterized by increased systemic inflammation which induces intrinsic B cell inflammation, measured by intracellular (ic) TNF-α, and this significantly decreases the capacity of the same B cells to make protective antibodies in response to vaccination (3). Other marker of B cell intrinsic inflammation is micro-RNA (miR) expression, particularly miR-16 and miR-155, which is increased in elderly B cells and negatively correlated with B cell function (4).
Objectives Our goal for this study was to evaluate B cell phenotype and function in RA patients treated Methotrexate (MTX), alone or together with anti-TNF-α. We hypothesized that patients treated with anti-TNF-α will show improved B cell function due to reduction in icTNF-α.
Methods We recruited 9 RA patients, 5 patients on MTX and 4 on MTX/anti-TNF-α. We measured the relevant B cell subsets in blood (Naïve, switched memory, IgM memory and late memory) by flow cytometry. Staining was performed with antibodies specific for CD19, CD27 and IgD. In addition, we isolated blood B cells using magnetic beads, and measured the expression of miR-16 and miR-155 on blood B cells by qPCR.
Results Preliminary data showed that the percentages of switched memory (IgD-CD27+) B cells are significantly higher (p<0.003) in patients undergoing MTX/anti-TNF-α therapy. We also observed a significant decrease in naïve B cell percentages (p<0.028). Preliminary results also showed a decrease in the mRNA expression of both miR-16 and miR-155 in patients on combination therapy compared to MTX alone.
Conclusions These results support the hypothesis that therapy with anti-TNF-α is beneficial for improving B cell function in RA patients, as compared to MTX therapy alone. Future experiments will seek to evaluate intrinsic B cell TNF levels in these patients and correlate them with measurements of B cell function. Treatment with anti-TNF-α may be able to block the excessive amounts of systemic TNF-α and in turn B cell intrinsic TNF-α which could improve the antibody responses and the risk of infections in RA patients undergoing therapy.
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Frasca, D., M. Romero, A. Diaz, S. Alter-Wolf, M. Ratliff, A. M. Landin, R. L. Riley, and B. B. Blomberg. 2012. A Molecular Mechanism for TNF-alpha-Mediated Downregulation of B Cell Responses. J Immunol 188: 279–286.
Frasca, D., A. Diaz, M. Romero, F. Ferraci, and B. B. Blomberg. 2015. MicroRNAs miR-155 and miR-16 Decrease AID and E47 in B Cells from Elderly Individuals. J. Immunol.195 (5): 2134–2140.
Disclosure of Interest None declared