Jo-1 autoantigen-specific B cells are skewed towards distinct functional B cell subsets in anti-synthetase syndrome patients

Peripheral Blood Lymphocyte Subsets and Heterogeneity of B Cell Subsets in Patients of Idiopathic Inflammatory Myositis with Different Myositis-specific Autoantibodies

Idiopathic inflammatory myopathies (IIM) are a group of myopathies that present with muscle weakness and multiple extra-muscular manifestations, in which lymphocytes play central roles in myositis pathogenesis. This study aimed to explore the clinical characteristics of lymphocyte subsets, especially B cell subsets, in patients with IIM. Our study included 176 patients with active IIM and 210 gender/age-matched healthy controls (HCs). Compared to HCs, patients have reduced counts of T cells, B cells, and natural killer cells. In addition, B cell subsets from 153 patients with IIM and 92 HCs were characterized. Patients had a lower percentage of memory B cells and translational memory B cells, while those patients were with an elevated percentage of CD19+ B cells, plasmablast and naïve B cells compared with HCs. Moreover, to further explore the heterogeneity of B cells in IIM, patients were categorized into three clusters based on clustering analysis. Cluster 1 was dominated by CD19+ B cells, Bregs and naïve B cells, cluster 3 was dominated by memory B cells and plasmablast, and cluster 2 had the highest proportion of translational memory B cells. Notably, patients in cluster 1 presented with higher CK levels, indicating muscle damage, whereas patients in cluster 3 showed a higher incidence of chest tightness. Our study indicated that lymphopenia is a common manifestation in patients with IIM. B cell subsets are abnormally expressed and showed high heterogeneity in patients with IIM. The patients with IIM were divided into three different clusters with different percentages of chest tightness and distinct CK levels.

Immune cell profiles of idiopathic inflammatory myopathy patients expressed anti-aminoacyl tRNA synthetase or anti-melanoma differentiation-associated gene 5 autoantibodies

BACKGROUND

Patients with idiopathic inflammatory myopathy (IIM) often express a different type of myositis-specific autoantibodies (MSAs), each associated with different clinical symptoms. Understanding the immunopathogenesis of various IIM subgroups can help improve the diagnosis and prognosis of IIM patients with different MSAs. However, the immune cell profiles of these IIM patients with anti-aminoacyl tRNA synthetase (ARS) or anti-melanoma differentiation-associated gene 5 (MDA5) autoantibodies remain unclear. We focused on the immune cell profiles of IIM patients with anti-ARS or anti-MDA5 autoantibodies.

RESULTS

The peripheral blood from IIM patients with anti-MDA5 autoantibody (MDA5 + group, n = 24) or one of the anti-ARS autoantibodies (ARS + group, n = 40) autoantibodies, and healthy controls (HC group, n = 60) were collected and examined. We found that IIM patients had a lower CD3 T cell population compared to the HC group. IIM patients showed a significantly lower TN cell population and a higher TEMRA cell population. Higher Th17 and Treg cell populations were found in these IIM patients than in the HC group. In these IIM patients, the MDA5 + group exhibited the higher percentages of Th17 and Treg cells than the ARS + group. It is noteworthy that the percentage of Th1 cells in the survival subgroup was higher than in the death subgroup in IIM patients with ARS + or MDA5 + . Furthermore, in the MDA5 + group, the percentage of Treg cells was higher in the survival subgroup compared to the death subgroup.

CONCLUSIONS

Our study demonstrated that elevated Th1 may be a good prognostic indicator in IIM patients with ARS + or MDA5 + . Elevated Treg may also help predict a good prognosis in MDA5 + IIM patients. However, more large-scale studies and clinical samples are needed to verify the significance of Th1 and Treg cell subsets in clinical outcomes for these IIM patients with ARS + or MDA5 + . These data may help design a therapeutic approach that specifically targets the pathogenic immune molecular responsible for autoimmune attacks in IIM.

Skeletal muscle fibers produce B-cell stimulatory factors in chronic myositis

Introduction

We aimed to identify B-cell-mediated immunomechanisms in inclusion body myositis (IBM) and polymyositis (PM) as part of the complex pathophysiology.

Materials and methods

Human primary myotube cultures were derived from orthopedic surgery. Diagnostic biopsy specimens from patients with IBM (n=9) and PM (n=9) were analyzed for markers of B cell activation (BAFF and APRIL) and for chemokines that control the recruitment of B cells (CXCL-12 and CXCL-13). Results were compared to biopsy specimens without myopathic changes (n=9) and hereditary muscular dystrophy (n=9).

Results

The mRNA expression of BAFF, APRIL, and CXCL-13 was significantly higher in IBM and PM compared to controls. Patients with IBM displayed the highest number of double positive muscle fibers for BAFF and CXCL-12 (48%) compared to PM (25%), muscular dystrophy (3%), and non-myopathic controls (0%). In vitro, exposure of human myotubes to pro-inflammatory cytokines led to a significant upregulation of BAFF and CXCL-12, but APRIL and CXCL-13 remained unchanged.

Conclusion

The results substantiate the hypothesis of an involvement of B cell-associated mechanisms in the pathophysiology of IBM and PM. Muscle fibers themselves seem to contribute to the recruitment of B cells and sustain inflammation.

High-Dimensional Analysis Reveals Distinct Endotypes in Patients With Idiopathic Inflammatory Myopathies

The idiopathic inflammatory myopathies (IIM) are a rare clinically heterogeneous group of conditions affecting the skin, muscle, joint, and lung in various combinations. While myositis specific autoantibodies are well described, we postulate that broader immune endotypes exist in IIM spanning B cell, T cell, and monocyte compartments. This study aims to identify immune endotypes through detailed immunophenotyping of peripheral blood mononuclear cells (PBMCs) in IIM patients compared to healthy controls. We collected PBMCs from 17 patients with a clinical diagnosis of inflammatory myositis and characterized the B, T, and myeloid cell subsets using mass cytometry by time of flight (CyTOF). Data were analyzed using a combination of the dimensionality reduction algorithm t-distributed stochastic neighbor embedding (t-SNE), cluster identification, characterization, and regression (CITRUS), and marker enrichment modeling (MEM); supervised biaxial gating validated populations identified by these methods to be differentially abundant between groups. Using these approaches, we identified shared immunologic features across all IIM patients, despite different clinical features, as well as two distinct immune endotypes. All IIM patients had decreased surface expression of RP105/CD180 on B cells and a reduction in circulating CD3+CXCR3+ subsets relative to healthy controls. One IIM endotype featured CXCR4 upregulation across all cellular compartments. The second endotype was hallmarked by an increased frequency of CD19+CD21loCD11c+ and CD3+CD4+PD1+ subsets. The experimental and analytical methods we describe here are broadly applicable to studying other immune-mediated diseases (e.g., autoimmunity, immunodeficiency) or protective immune responses (e.g., infection, vaccination).

Lymphocyte immunophenotyping in inflammatory myositis: a review

PURPOSE OF REVIEW

This is a comprehensive review of the current knowledge on predominant immune cell phenotypes involved in idiopathic inflammatory myopathies (IIM).

RECENT FINDINGS

Major circulating immune cell subpopulations described in IIM encompass the lymphocyte compartment. An unbalance in T cell subsets seems to consistently affect the peripheral and muscle compartment, with a predominance of CD4+ T and B cells in dermatomyositis, CD8+ T cells in polymyositis/inclusion body myositis (IBM) and novel findings highlighting novel proinflammatory T subsets, that is, CD8+Tbet+ and CD28- T cells across different IIM subsets. On the other hand, an impairment in Treg cells number and function has been described especially across polymyositis/dermatomyositis and IBM. Total T follicular helper (Tfh) cells, increased in immune-mediated necrotizing myopathy, skewed toward Tfh2 and Tfh17 in dermatomyositis, polymyositis, and juvenile dermatomyositis. B cell compartment is more rarely described in IIM, yet an unbalance in this pool is as well likely. Evidence of plasma cells increased in polymyositis, dermatomyositis, IBM, and Bregs decreased in dermatomyositis have been reported. Perturbations in the memory and naïve subsets are common in dermatomyositis/polymyositis and antisynthetase syndrome.

SUMMARY

Protean immune cell abnormalities characterize different IIM subsets, reflecting the complexity of these autoimmune conditions. A deeper understanding of B-cell and T-cell immunophenotyping may promote early diagnosis and identification of new potential therapeutic targets.

High-Throughput Detection of Autoantigen-Specific B Cells Among Distinct Functional Subsets in Autoimmune Donors

Antigen-specific B cells (ASBCs) can drive autoimmune disease by presenting autoantigen to cognate T cells to drive their activation, proliferation, and effector cell differentiation and/or by differentiating into autoantibody-secreting cells. Autoantibodies are frequently used to predict risk and diagnose several autoimmune diseases. ASBCs can drive type 1 diabetes even when immune tolerance mechanisms block their differentiation into antibody-secreting cells. Furthermore, anti-histidyl tRNA synthetase syndrome patients have expanded IgM⁺ Jo-1-binding B cells, which clinically diagnostic IgG Jo-1 autoantibodies may not fully reflect. Given the potential disconnect between the pathologic function of ASBCs and autoantibody secretion, direct study of ASBCs is a necessary step towards developing better therapies for autoimmune diseases, which often have no available cure. We therefore developed a high-throughput screening pipeline to 1) phenotypically identify specific B cell subsets, 2) expand them in vitro, 3) drive them to secrete BCRs as antibody, and 4) identify wells enriched for ASBCs through ELISA detection of antibody. We tested the capacity of several B cell subset(s) to differentiate into antibody-secreting cells following this robust stimulation. IgM⁺ and/or IgD⁺, CD27^- memory, memory, switched memory, and B_ND B cells secreted B cell receptor (BCR) as antibody following in vitro stimulation, whereas few plasmablasts responded. Bimodal responses were observed across autoimmune donors for IgM⁺ CD21^lo and IgM^- CD21^lo B cells, consistent with documented heterogeneity within the CD21^lo subset. Using this approach, we detected insulin-binding B cell bias towards CD27^- memory and CD27⁺ memory subsets in pre-symptomatic type 1 diabetes donors. We took advantage of routine detection of Jo-1-binding B cells in Jo-1+ anti-histidyl tRNA synthetase syndrome patients to show that Jo-1-binding B cells and total B cells expanded 20-30-fold using this culture system. Overall, these studies highlight technology that is amenable to small numbers of cryopreserved peripheral blood mononuclear cells that enables interrogation of phenotypic and repertoire attributes of ASBCs derived from autoimmune patients.