IntroductionClinical trials revealed a high efficacy of mycophenolate mofetil (MMF) in inducing and maintaining remission in patients with class III-V-lupus nephritis. Also extrarenal manifestations respond to MMF treatment. However, few attempts have been undertaken to delineate its mechanism of action in systemic lupus erythematosus (SLE) a disease characterized by enhanced B cell activation.MethodsClinical and paraclinical parameters of 107 patients with SLE were recorded consecutively and analyzed retrospectively. Patients were divided into treatment groups (MMF: n = 39, azathioprine (AZA) n = 30 and controls without immunosuppressive therapy n = 38). To further delineate the effect of mycophenolic acid (MPA) on naive and memory B cells in vitro assays were performed.ResultsAlthough patients taking AZA flared more frequently than patients on MMF or controls, the analysis of clinical parameters did not reveal significant differences. However, profound differences in paraclinical parameters were found. B cell frequencies and numbers were significantly higher in patients taking MMF compared to those on AZA but lower numbers and frequencies of plasmablasts were detected compared to AZA-treated patients or controls. Notably, MMF treatment was associated with a significantly higher frequency and number of transitional B cells as well as naive B cells compared to AZA treatment. Differences in T cell subsets were not significant. MPA abrogated in vitro proliferation of purified B cells completely but had only moderate impact on B cell survival.ConclusionsThe thorough inhibition of B cell activation and plasma cell formation by MMF might explain the favorable outcomes of previous clinical trials in patients with SLE, since enhanced B cell proliferation is a hallmark of this disease.

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IntroductionDisease activity and therapy show an impact on cellular and serological parameters in patients with systemic lupus erythematosus (SLE). This study was performed to compare the influence of mycophenolate mofetil (MMF) and cyclophosphamide (CYC) therapy on these parameters in patients with flaring, organ-threatening disease.MethodsSLE patients currently receiving CYC (n = 20), MMF (n = 25) or no immunosuppressive drugs (n = 22) were compared using a cross-sectional design. Median disease activity and daily corticosteroid dose were similar in these treatment groups. Concurrent medication, organ manifestations, and disease activity were recorded, and cellular and serological parameters were determined by routine diagnostic tests or flow cytometric analysis. In addition follow-up data were obtained from different sets of patients (CYC n = 24; MMF n = 23).ResultsAlthough both drugs showed a significant effect on disease activity and circulating B cell subsets, only MMF reduced circulating plasmablasts and plasma cells as well as circulating free light chains within three months of induction therapy. Neither MMF nor CYC were able to reduce circulating memory B cells. MMF lowered IgA levels more markedly than CYC. We did not observe a significant difference in the reduction of IgG levels or anti-dsDNA antibodies comparing patients receiving MMF or CYC. In contrast to MMF, induction therapy with CYC was associated with a significant increase of circulating CD8+ effector T cells and plasmacytoid dendritic cells (PDCs) after three months.ConclusionsThe results indicate differences between MMF and CYC with regard to the mechanism of action. MMF, but not CYC, treatment leads to a fast and enduring reduction of surrogate markers of B cell activation, such as circulating plasmablasts, plasma cells and free light chains but a comparable rate of hypogammaglobulinemia.Electronic supplementary materialThe online version of this article (doi:10.1186/s13075-015-0603-8) contains supplementary material, which is available to authorized users.

Background B cell hyperactivity is a hallmark of SLE. Differential blood counts, lymphocyte subsets and serological parameters are affected by disease activity and therapy. Objectives To analyze the influence of MMF and other immunosuppressive drugs (ID) such as cyclophosphamide (CYC), azathioprine (AZA) or methotrexate (MTX) on B cell and PB/PC counts and FLCκ/λ levels. Methods We performed a retrospective cross-sectional analysis of cellular and serological parameters in patients with SLE. Lupus patients with comparably high disease activity and either on induction or on maintenance therapy were subdivided into different treatment groups and compared to activity-matched patients not on ID (Tab. 1). All parameters were also determined repeatedly after induction therapy with CYC (n=24) or MMF (n=23) and in another subset of patients with MMF-responsive quiescent disease during drug taper or withdrawel (n=27). Table 1 B cells/μl Plasmablasts/plasma FLCκ FLCλ cells/μl (mg/l) (mg/l) Induction therapy  MMF (n=41) 81.4* 1.0****^^^^ 17.5**^ 22.3* (2.8–365.0) (0.0–11.7) (8.9–151.0) (10.0–150.0)  CYC (n=23) 32.5*°°° 7.3**** 34.9** 30.2* (4.8–206.1) (0.1–90.9) (1.6–246.0) (4.1–153.0)  Controls (n=39) 118.2°°° 3.8^^^^ 26.4^ 28.0 (14.7–1020.0) (0.5–61.4) 26.4^ 28.0 Maintenance therapy  MMF (n=53) 98.8*** 0.9**^^^^ 17.1^^ 19.3^ (0.8–553.4) (0.0–11.7) (8.9–151.0) (10.4–150.0)  AZA (n=41) 39.1***§ § § § 2.4** 22.0 22.0 (4.7–152.4) (0.0–18.7) (7.9–152.0) (1.2–142.0)  MTX (n=19) 52.2° 1.1°° 30.1 20.6 (16.5–317.8) (0.2–15.1) (8.5–89.9) (6.8–77.0)  Controls (n=51) 124.3§ § § §° 4.4^^^^°° 25.1^^ 27.1^ (14.7–1020.0) (0.4–61.4) (9.2–66.8) (11.9–127.0) Results are presented as median (range); statistically significant differences (Dunn's multiple comparisons test): one (p<0.05), two (p<0.01), three (p<0.001), four (p<0.0001) symbols *°^§. Results Patients undergoing induction therapy with MMF had significantly lower PB/PC counts compared to patients treated with CYC or controls. In patients receiving maintenance therapy MMF was associated with a significantly lower PB/PC count compared to AZA and no ID. In addition PB/PC counts were also significantly lower in patients undergoing MTX treatment compared to controls. Consistent with these findings patients receiving MMF had significantly lower FLCκ serum levels compared to patients with CYC induction or controls. Patients receiving MMF to maintain remission had significantly lower FLC serum levels than controls, whereas AZA had no influence on FLC (Tab.1). A drastic decrease of FLCκ (p<0.0007), FLCλ (p=0.0017), and PB/PC counts (p<0.0001) was detected in patients who had been on MMF for 16 (10 to 65) weeks. In contrast, no significant change in FLC levels or PB/PC counts was noted 15 (10 to 39) weeks after starting CYC. Inversely, an increase of PB/PC counts was observed 92 (14 to 191) weeks after MMF had been tapered or discontinued (p<0.0001). In the latter patients we also observed rising FLC levels, but this was ...

Background Rheumatoid arthritis (RA) is a chronic inflammatory autoimmune disease characterized by the presence of autoantibodies (AA) such as rheumatoid factor (RF) and anti-citrullinated peptide antibodies (ACPAs). These AA do not only play a pivotal role in diagnostics, but also in pathogenesis of RA. AA can be secreted by long-lived plasma cells homing to the bone marrow or by newly generated plasma cells derived from the memory B cell pool. Objectives To determine the frequency of ACPA-specific cells within the circulating memory B cell pool of ACPA-positive RA patients. Methods In order to compare the frequency of anti-cyclic citrullinated peptid (CCP) and anti-mutated citrullinated vimentin (MCV) antibody specific B cells within the memory B cell pool of 7 CCP- and 7 MCV-positive patients with RA and 4 or 6 normal healthy subjects (NHS) we analyzed antibody secretion by ELISPOT after transforming memory B cells into plasmablasts (PB). For comparison we determined the frequency of tetanus toxoid (TT)-specific B cells in the circulating pool of memory B cells of 8 TT-vaccinated NHS. CD27+ memory B cells were isolated from peripheral blood samples. After polyclonal activation for 4 days the percentage of PB (CD27++) was determined by flow cytometry. To determine the frequency of anti-CCP, anti-MCV and anti-TT antibody secreting cells ELISPOT assays (IgM, IgG, IgA) were performed. Results Flow cytometric analysis revealed that after 4 days 62±11% (RA n=14) and 62±13% (NHS n=18) of all viable cells in culture adopted the phenotype of CD27++ PB. The frequencies of antigen-specific B cells of all individuals are shown in Table 1. In contrast to NHS, 71.4% of CCP-positive and 28.6% of all MCV-positive RA patients had detectable frequencies of CCP- or MCV-specific IgG antibody secreting cells (ASC). In these individuals the frequencies of ACPA-secreting cells were lower than the frequency of anti-TT-specific IgG ASC in TT-vaccinated NHS, who all had detectable frequencies of TT-specific IgG ASC (CCP: 0.22±0.21%, MCV: 0.34±0.40, TT: 0.9±0.7). Table 1.Frequency of antigen-specific spots in relation to total IgM, IgG and IgA spots Antigen Isotype % Spots (mean ± SD) CCP+ or MCV+ RA NHS (CCP n=7; MCV n=7) (CCP n=4: MCV n=6; TT n=8) CCP IgM 0.17±0.31 0.07±0.04 IgG 0.16±0.20 0.0007±0.001 IgA 0.04±0.06 0.03±0.02 MCV IgM 0.11±0.15 0.07±0.10 IgG 0.10±0.20 0.004±0.01 IgA 0.05±0.10 0.02±0.04 TT IgM na 0.3±0.5 IgG na 0.9±0.7 IgA na 0.007±0.02 CCP, cyclic citrullinated peptid; MCV, mutated citrullinated vimentin; TT, tetanus toxoid; NHS, normal healthy subjects; na, not applicable. Conclusions Using this approach, ACPA-specific B cells can be detected in the circulating memory B cell pool only in a subset of ACPA-positive RA patients. In the remaining patients, ACPA-specific B or plasma cells might home in the bone marrow or inflamed joints. Disclosure of Interest U. Saunders Grant/research support: Chugai Pharmaceutical Co., Ltd., T. Fassbinder: None declared, H. Becker: No...