Maiko Yoshikawa

Activation of Syk in peripheral blood B cells in patients with rheumatoid arthritis: a potential target for abatacept therapy.

B cells play a pivotal role in the pathogenesis of autoimmune diseases. Although Syk functions as a key molecule in B cell receptor signaling, the pathologic role of Syk in B cells in rheumatoid arthritis (RA) remains unclear. The purpose of this study was to assess the relevance of activation of Syk in B cells to the pathologic development of RA and to the responsiveness of RA patients to treatment with biologics.

Amplification of IL-21 signalling pathway through Bruton’s tyrosine kinase in human B cell activation

OBJECTIVE B cells play an important role in the pathogenesis of autoimmune diseases. The role of Brutons tyrosine kinase (Btk) in cytokine-induced human B cell differentiation and class-switch recombination remains incompletely defined. This study analysed the effect of Btk on human activated B cells. METHODS Purified B cells from healthy subjects were stimulated with B cell receptor (BCR) and other stimuli with or without a Btk inhibitor and gene expression was measured. The B cell line BJAB was used to assess Btk-associated signalling cascades. Phosphorylated Btk (p-Btk) in peripheral blood B cells obtained from 10 healthy subjects and 41 patients with RA was measured by flow cytometry and compared with patient backgrounds. RESULTS IL-21 signalling, in concert with BCR, CD40 and BAFF signals, led to robust expression of differentiation- and class-switch DNA recombination-related genes and IgG production in human B cells, all of which were significantly suppressed by the Btk inhibitor. Although phosphorylation of STAT1 and STAT3 was induced by co-stimulation with IL-21, BCR and CD40, STAT1 phosphorylation in the nucleus, but not in the cytoplasm, was exclusively impaired by Btk blockade. High levels of p-Btk were noted in B cells of RA patients compared with controls and they correlated significantly with titres of RF among RF-positive patients. CONCLUSION The findings elucidate a model in which Btk not only plays a fundamental role in the regulation of BCR signalling, but may also mediate crosstalk with cytokine signalling pathways through regulation of IL-21-induced phosphorylation of STAT1 in the nuclei of human B cells. Btk appears to have pathological relevance in RA.

Increased Syk phosphorylation leads to overexpression of TRAF6 in peripheral B cells of patients with systemic lupus erythematosus

Objective Activation of B cells is a hallmark of systemic lupus erythematosus (SLE). Syk and TRAF6 are key signaling molecules in B-cell activation through BCR and CD40/TLR, respectively. Nevertheless, whether expression of Syk and TRAF6 is altered in SLE B cells remains unknown. Methods Phosphorylation and/or expression of Syk and TRAF6 were analyzed by flow cytometry in peripheral blood mononuclear cells isolated from SLE patients. Results Pronounced phosphorylation and expression of Syk were noted in B cells from SLE patients compared with healthy donors. Levels of Syk phosphorylation correlated with the disease activity score. TRAF6 was significantly over-expressed in B cells of SLE patients as compared with healthy donors, and significant correlation of levels of TRAF6 expression and Syk phosphorylation was observed in SLE patients. Levels of TRAF6 expression were more pronounced in CD27+ memory B cells than in CD27-naïve B cells. In vitro treatment of SLE B cells with a Syk inhibitor (BAY61-3606) reduced Syk phosphorylation as well as TRAF6 expression. Conclusion Our results suggest that the activated Syk-mediated TRAF6 pathway leads to aberrant activation of B cells in SLE, and also highlight Syk as a potential target for B-cell-mediated processes in SLE.

Correlation of T follicular helper cells and plasmablasts with the development of organ involvement in patients with IgG4-related disease

Objective To assess the role of an abnormal immune network in the pathology of IgG4-related disease (IgG4-RD). Methods Sixteen patients diagnosed with IgG4-RD at our institution were selected. Peripheral immunocompetent cells were immunophenotyped by multicolour flow cytometry to assess the association between clinical manifestation and pathological findings. Results Compared with healthy controls, IgG4-RD patients showed comparable proportions of Th1 and Th17 cells, but higher proportions of Treg and follicular helper T (Tfh) cells. Further, the proportions of class-switched memory B cells and plasmablasts were higher in patients. Among all phenotypes, in particular, the plasmablast proportion increased from 4.2% (controls) to 16.5% (patients). The serum IgG levels were found to be correlated with the proportions of plasmablasts and Tfh cells, but not with those of other T cell subsets. In patients with extraglandular symptoms, only plasmablasts, Tfh cells and memory Treg cells were increased. Histopathological examination revealed a marked Tfh (CD4+ Bcl6+) cell infiltration; the increase of Tfh cells in the peripheral blood thus reflected the degree of Tfh cell infiltration into the tissue. Although steroid therapy reduced plasmablast and Tfh cell proportions, the memory Treg cell proportion remained unchanged. Conclusion The association found between Tfh cells and plasmablasts, linked with biological plausibility, suggests that Tfh cells contribute to the pathogenesis of IgG4-RD. Our results also suggested that controlling the Tfh cell-plasmablast axis could be a novel therapeutic strategy for treating IgG4-RD.

Differential effects of biological DMARDs on peripheral immune cell phenotypes in patients with rheumatoid arthritis

Objective The aim of this study was to assess the therapeutic effects of biological DMARDs (bDMARDs) on the diversity of immune cell phenotypes in peripheral blood of patients with RA. Methods Peripheral immune cell phenotypes were determined in 108 RA patients who were non-responsive to conventional DMARDs and 33 healthy control subjects by eight-colour flow cytometry. We also examined the correlation between the phenotypes and clinical findings and assessed the effects of 24-week treatment with bDMARDs. Results The proportions of T follicular helper (Tfh) cells, IgD- CD27- double negative B cells and plasmacytoid dendritic cells (pDCs) were higher in patients with active RA than in healthy control. The percentages of memory T cells, Th17 and Tfh cells correlated with autoantibody titres, whereas that of plasmablasts correlated with disease activity scores. Treatment with TNF inhibitors reduced the proportion of pDCs, while tocilizumab reduced the proportion of double-negative B cells but increased naïve and activated Treg cells. Abatacept treatment resulted in marked decrease in the proportion of activated Tfh but slightly reduced Th17 and Treg cells. The proportion of Tfh cells was an independent and significant predictor of the response to abatacept therapy. Conclusion Molecular targeted therapies induced different changes in different immune cell phenotypes. Among the phenotypes, Tfh cells seem a potential target for abatacept. Immunophenotypic analysis might be useful for prediction of the response to bDMARDs.

Peripheral immunophenotyping identifies three subgroups based on T cell heterogeneity in lupus patients

To elucidate the diversity of systemic lupus erythematosus (SLE) based on immunophenotyping.

Precision medicine using different biological DMARDs based on characteristic phenotypes of peripheral T helper cells in psoriatic arthritis

Objectives We sought to investigate the selection of specific biological DMARDs (bDMARDs) based on characteristic lymphocyte phenotypes for treating PsA. Methods Of 64 patients with PsA resistant to MTX, 26 underwent bDMARDs therapy selected according to phenotypic differences in peripheral helper T cells on 8-colour flow cytometry. The efficacies of this strategic treatment and the standard treatment administered to the other 38 patients were evaluated at 6 months. Results The 26 patients with PsA in the strategic treatment group were classified into the following four types based on peripheral blood analysis: (i) CXCR3+CCR6-CD38+HLA-DR+ activated Th1 cell-predominant type, (ii) CXCR3-CCR6+ CD38+HLA-DR+ activated Th17 cell-predominant type, (iii) Th1/Th17-high type and (iv) Th1/Th17-low type. Accordingly, ustekinumab was administered to the activated Th1 cell-predominant patients, secukinumab to the activated Th17 cell-predominant patients, secukinumab or TNF inhibitor to the Th1/Th17-high patients, and TNF inhibitor to the Th1/Th17-low patients. After 6 months of strategic treatment, there was a significant decrease in simplified disease activity index (SDAI) (from 16.2 to 3.52), DAS28 (ESR) (from 4.13 to 2.27) and psoriasis area and severity index (from 8.36 to 2.40). Low disease activity by SDAI was achieved in 24 (92.3%) of the 26 patients. The rate of low disease activity achievement according to SDAI at 6 months was significantly higher in the strategic bDMARDs treatment group compared with that of the standard bDMARDs treatment group. Conclusion Strategic treatment in which different bDMARDs were selected according to phenotypic differences in helper T cells showed significantly higher efficacy than standard bDMARD therapy, indicating the value of precision medicine.

Efficacy and safety of anti-CD20 antibody rituximab for patients with refractory systemic lupus erythematosus:

Objective We examined the efficacy and safety of rituximab in patients with refractory systemic lupus erythematosus (SLE). Methods The study enrolled 63 SLE patients who were treated with rituximab between 2002 and 2015. The participants underwent a battery of tests before treatment and at one year. Treatment ranged from two to four times at 500 or 1000 mg. Results Baseline characteristics were males:females = 6:57, age 33.9 years, and disease duration 87.2 months. The primary endpoint: The rate of major clinical response (MCR) was 60% while the partial clinical response (PCR) was 25%. Thirty of 36 (83%) patients with lupus nephritis (WHO II: 2, III: 5, IV: 22, V: 4, IV+V: 2, not assessed: 1) and 22 of 24 patients (92%) with neuropsychiatric SLE, who could be followed at one year, showed changes from BILAG A or B score to C or D score at one year. Multivariate analysis identified high anti-dsDNA antibody and shorter disease duration as significant determinants of MCR at one year. Repeat examination was conducted at five years. Primary failure was recorded in 8.8% and secondary failure in 32.4% (time to relapse: 24.4 months). Rituximab was well tolerated although 65 adverse events, mostly infections, were recorded within one year. Conclusion Rituximab is potentially efficacious for the treatment of patients with refractory SLE.

A case of refractory lupus nephritis complicated by psoriasis vulgaris that was controlled with secukinumab

It has been reported that T helper 17 cells are involved in the pathogenesis of systemic lupus erythematosus, but there is no report on interleukin-17-targeted therapy. We report a case of a 62-year-old female who presented with psoriasis vulgaris and refractory lupus nephritis. Because her conditions were resistant to conventional treatment, and flow cytometry confirmed the proliferation of activated T helper 17 cells in peripheral blood, and examination of a renal biopsy tissue sample confirmed infiltration of numerous interleukin-17-positive lymphocytes to the renal interstitium, administration of the anti-interleukin-17A antibody secukinumab was initiated. After starting secukinumab the clinical and biological features were improved.

B cell phenotypes, signaling and their roles in secretion of antibodies in systemic lupus erythematosus

B cells play a pivotal role in the initiation and perpetuation of SLE. Because SLE is molecularly and clinically heterogeneous, efficacious targeted therapy to clinical remission has not yet been established in SLE. We have found i) statistical clustering between Tfh cells and class-switched memory B cells and the upregulated transition from CXCR5+ IgM memory B cells to CXCR3+ class-switched memory B cells in SLE by 8-color flow cytometry, ii) the involvement of Syk, Btk and JAK in the activation and differentiation of B cells in SLE, iii) SLE patients was divided to 3 groups based on immunophenotypic analysis and statistical analysis and patients in the Tfh/class-switched B cell-dominant group were most refractory to conventional therapies although 3 groups had similar clinical features. Thus, novel therapies targeting Tfh-memory B cell interaction are anticipated in certain subpopulation of SLE patients, which leads to the precision medicine in SLE.