We found a significant decrease in mutational frequency of the B cell receptor (BCR) at week 12, 24 and over a year during TCZ therapy (Figure?3A). cells. DN B cells carry rearranged heavy chain gene sequences with a diversified mutational pattern consistent with memory B cells. In contrast to tumor necrosis factor alpha (TNF-) inhibition, a significant reduction in mutational frequency of BCR gene rearrangements at week 12, 24 and 1?year ( 0.0001) was observed by IL-6R inhibition. These changes were observed for all BCR isotypes TAK-700 (Orteronel) IgG, IgA and IgM at week 12, 24 and 1?year ( 0.0001). IgA-RF, IgA serum level and IgA+ DN B cells decreased significantly ( 0.05) at week 12 and week 24 during TCZ. Patients with a good European League Against Rheumatism (EULAR) response to TCZ had less DN B cells at baseline as compared to moderate responders (differentiation of B cells into antibody-forming cells and germinal center reactions. In addition to its involvement in immune responses, it also regulates hematopoiesis, the acute phase response and inflammation. Dysregulation of IL-6 production and its pathological role in different autoimmune diseases have been well documented and highlight IL-6 and its signaling cascade as a potential target for autoimmune therapy [9-13]. Consequently, tocilizumab (TCZ), a humanized anti-IL-6 receptor (IL-6R) monoclonal antibody (mAb) against the alpha chain of IL-6R, which prevents binding of IL-6 to membrane and soluble IL-6R, was developed and has been licensed for the treatment of RA [14]. TCZ has shown convincing clinical efficacy by reduction of signs/symptoms and a marked inhibition of radiological progression [11]. Functionally distinct B cell subsets can be TAK-700 (Orteronel) defined by the phenotype expression of CD27 and immunoglobulin D (IgD). Human peripheral memory B cells are mainly discriminated from na?ve B CDKN2D cells by the phenotypic expression of CD27 (a member of the tumor necrosis factor receptor (TNFR) family) and presence of somatic hypermutation (SHM) in their Ig variable genes [15,16]. CD27 expression by B cells has been considered a hallmark for SHM and their memory. CD27+ memory B cells are a heterogeneous population comprising of pre-switch (IgD?+?CD27+) and post-switch (IgD-CD27+) B cell subsets [13,17,18]. There are still unanswered questions about the exact identification of memory B cells based on CD27 expression, since recent studies in these lines have shown a double-negative (DN) population (CD19?+?CD27-IgD-) that bears all signatures of memory B cells [19-21] (Figure?1A). A very large portion of DN (CD27-IgD-) B cells express mutated Ig and an evaluation of telomere length, expression of the anti-apoptotic molecule Bcl2, and absence of the ATP-binding cassette B1 transporter (ABCB1) have been used to discriminate them from na?ve CD27- B cells and relate them to the memory B cell compartment [22,23]. Even though DN memory B cells mainly express switched Ig isotypes, they have a reduced rate of SHM compared to post-switch B cells. This has been hypothesized to TAK-700 (Orteronel) be due to either an impaired germinal center (GC) formation or resembling a distinct lineage of memory B cells [23,24]. In systemic lupus erythematosus (SLE), DN B cells are expanded and could be linked to autoimmunity by analysis of the specific autoantibodies including 9G4 expression [19]. So far, the nature of DN B cells has still not been fully delineated in general as well as in autoimmune diseases. Open in a separate window Figure 1 Phenotype analysis of CD27-IgD- B cells in RA patients and their relation to EULAR response. (A) Representative FACS plot. Characterization of (CD27-IgD-) DN B cells, PS?=?post-switch (CD27?+?IgD-), Pre?=?pre-switch (CD27?+?IgD+) and na?ve (CD27-IgD+) B cells. (B) Comparison of DN B cells in RA patients and HD. DN B cells in RA patients (n?=?44) and HD (n?=?45) show a significantly higher percentage of the frequency of DN B cells in RA patients ( 0.0001). (C) TAK-700 (Orteronel) EULAR response to IL-6R inhibition. Week 12 EULAR good responders (BL DAS28?=?5.1??0.3) to TCZ have significantly (values were determined by Mann-Whitney test using GraphPad Prism 5. (*** 0.0001, ** 0.001 and * 0.05). BL DAS28, baseline disease activity score 28; DN, double-negative; EULAR, European League Against Rheumatism; HD,.
We found a significant decrease in mutational frequency of the B cell receptor (BCR) at week 12, 24 and over a year during TCZ therapy (Figure?3A)