Integrative Analysis Reveals a Molecular Stratification of Systemic Autoimmune Diseases

OBJECTIVE

Clinical heterogeneity, a hallmark of systemic autoimmune diseases, impedes early diagnosis and effective treatment, issues that may be addressed if patients could be classified into groups defined by molecular pattern. This study was undertaken to identify molecular clusters for reclassifying systemic autoimmune diseases independently of clinical diagnosis.

METHODS

Unsupervised clustering of integrated whole blood transcriptome and methylome cross-sectional data on 955 patients with 7 systemic autoimmune diseases and 267 healthy controls was undertaken. In addition, an inception cohort was prospectively followed up for 6 or 14 months to validate the results and analyze whether or not cluster assignment changed over time.

RESULTS

Four clusters were identified and validated. Three were pathologic, representing "inflammatory," "lymphoid," and "interferon" patterns. Each included all diagnoses and was defined by genetic, clinical, serologic, and cellular features. A fourth cluster with no specific molecular pattern was associated with low disease activity and included healthy controls. A longitudinal and independent inception cohort showed a relapse-remission pattern, where patients remained in their pathologic cluster, moving only to the healthy one, thus showing that the molecular clusters remained stable over time and that single pathogenic molecular signatures characterized each individual patient.

CONCLUSION

Patients with systemic autoimmune diseases can be jointly stratified into 3 stable disease clusters with specific molecular patterns differentiating different molecular disease mechanisms. These results have important implications for future clinical trials and the study of nonresponse to therapy, marking a paradigm shift in our view of systemic autoimmune diseases.

Pathogenic memory plasma cells in autoimmunity

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Memory plasma cells are long-lived but require specialized niches for their survival.

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Memory plasma cells are refractory to conventional immunosuppression.

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Pathogenic memory plasma cells represent ‘roadblocks’ to response to conventional therapy.

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Strategies for (selective) targeting of memory plasma cells are in preclinical and clinical tests.

The Maintenance of Memory Plasma Cells

It is now well accepted that plasma cells can become long-lived (memory) plasma cells and secrete antibodies for months, years or a lifetime. However, the mechanisms involved in this process of humoral memory, which is crucial for both protective immunity and autoimmunity, still are not fully understood. This article will address a number of open questions. For example: Is longevity of plasma cells due to their intrinsic competence, extrinsic factors, or a combination of both? Which internal signals are involved in this process? What factors provide external support? What survival factors play a part in inflammation and autoreactive disease? Internal and external factors that contribute to the maintenance of memory long-lived plasma cells will be discussed. The aim is to provide useful additional information about the maintenance of protective and autoreactive memory plasma cells that will help researchers design effective vaccines for the induction of life-long protection against infectious diseases and to efficiently target pathogenic memory plasma cells.

Proteasome inhibition with bortezomib induces a therapeutically relevant depletion of plasma cells in SLE but does not target their precursors

Long-lived plasma cells (PCs) not only provide protective humoral immunity, they are also an essential component of the autoreactive immunologic memory that may drive chronic immune responses in systemic autoimmunity, such as systemic lupus erythematosus (SLE). The therapeutic relevance of their targeting has been demonstrated in preclinical models and severe, treatment-refractory cases of autoimmune diseases using the proteasome inhibitor bortezomib. Herein, we describe in detail the dynamic serologic changes and effects on immune effector cells in eight SLE patients receiving a median two cycles of 1.3 mg/m² intravenous bortezomib. Upon proteasome inhibition, immunoglobulin levels gradually declined by ∼30%, associated with a significant reduction of autoantibodies, and serum complement whereas B-cell activation factor levels increased. While proteasome inhibition was associated with a significant depletion of short- and long-lived PCs in peripheral blood and bone marrow by ∼50%, including those with a distinctly mature CD19^- phenotype, their precursor B cells and T cells largely remained unaffected, resulting in a rapid repopulation of short-lived PCs after bortezomib withdrawal, accompanied by increasing autoantibody levels. Collectively, these findings identify proteasome inhibitors as a promising treatment option for refractory SLE, but also indicate that PC depletion needs to be combined with targeted B-cell therapies for sustained responses in systemic autoimmunity.

CXCR4-CXCL12 interaction is important for plasma cell homing and survival in NZB/W mice

Antibody-secreting cells (ASCs), including short-lived plasmablasts and long-lived memory plasma cells (LLPCs), contribute to autoimmune pathology. ASCs, particularly LLPCs, refractory to conventional immunosuppressive drugs pose a major therapeutic challenge. Since stromal cells expressing C-X-C motif chemokine-12 (CXCL12) organize survival niches for LLPCs in the bone marrow, we investigated the effects of CXCL12 and its ligand CXCR4 (C-X-C chemokine receptor 4) on ASCs in lupus mice (NZB/W). Fewer adoptively transferred splenic ASCs were retrieved from the bone marrow of recipient immunodeficient Rag1^-/- mice when the ASCs were pretreated with the CXCR4 blocker AMD3100. CXCR4 blockade also significantly reduced anti-OVA ASCs in the bone marrow after secondary immunization with OVA. In this study, AMD3100 efficiently depleted ASCs, including LLPCs. After two weeks, it decreased the total number of ASCs in the spleen and bone marrow by more than 60%. Combination with the proteasome inhibitor bortezomib significantly enhanced the depletion effect of AMD3100. Continuous long-term (five-month) CXCR4 blockade with AMD3100 after effective short-term LLPCs depletion kept the number of LLPCs in the bone marrow low, delayed proteinuria development and prolonged the survival of the mice. These findings identify the CXCR4-CXCL12 axis as a potential therapeutic target likely due to its importance for ASC homing and survival.

Analyzing pathogenic (double-stranded (ds) DNA-specific) plasma cells via immunofluorescence microscopy

Introduction

While protective plasma cells (PCs) are an important part of the individual’s immune defense, autoreactive plasma cells such as dsDNA-specific plasma cells contribute to the pathogenesis of autoimmune diseases like systemic lupus erythematosus (SLE). However, the research on dsDNA-specific plasma cells was restricted to the ELISpot technique, with its limitations, as no other attempt for identification of dsDNA-reactive plasma cells had been successful.

Methods

With improved fluorochrome labeling of dsDNA, removal of DNA aggregates, and enhanced blocking of unspecific binding, we were able to specifically detect dsDNA-reactive plasma cells by immunofluorescence microscopy.

Results

Via this novel technique we were able to distinguish short-lived (SLPCs) and long-lived (LLPCs) autoreactive plasma cells, discriminate dsDNA-specific plasma cells according to their immunoglobulin class (IgG, IgM, and IgA) and investigate autoreactive (dsDNA) and vaccine-induced ovalbumin (Ova) plasma cells in parallel.

Conclusions

The detection of autoreactive dsDNA-specific plasma cells via immunofluorescence microscopy allows specific studies on pathogenic and protective plasma cell subsets and their niches, detailed evaluation of therapeutic treatments and therefore offers new possibilities for basic and clinical research.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-015-0811-2) contains supplementary material, which is available to authorized users.

Long-lived plasma cells are early and constantly generated in New Zealand Black/New Zealand White F1 mice and their therapeutic depletion requires a combined targeting of autoreactive plasma cells and their precursors

Introduction

Autoantibodies contribute significantly to the pathogenesis of systemic lupus erythematosus (SLE). Unfortunately, the long-lived plasma cells (LLPCs) secreting such autoantibodies are refractory to conventional immunosuppressive treatments. Although generated long before the disease becomes clinically apparent, it remains rather unclear whether LLPC generation continues in the established disease. Here, we analyzed the generation of LLPCs, including autoreactive LLPCs, in SLE-prone New Zealand Black/New Zealand White F1 (NZB/W F1) mice over their lifetime, and their regeneration after depletion.

Methods

Bromodeoxyuridine pulse-chase experiments in mice of different ages were performed in order to analyze the generation of LLPCs during the development of SLE. LLPCs were enumerated by flow cytometry and autoreactive anti-double-stranded DNA (anti-dsDNA) plasma cells by enzyme-linked immunospot (ELISPOT). For analyzing the regeneration of LLPCs after depletion, mice were treated with bortezomib alone or in combination with cyclophosphamide and plasma cells were enumerated 12 hours, 3, 7, 11 and 15 days after the end of the bortezomib cycle.

Results

Autoreactive LLPCs are established in the spleen and bone marrow of SLE-prone mice very early in ontogeny, before week 4 and before the onset of symptoms. The generation of LLPCs then continues throughout life. LLPC counts in the spleen plateau by week 10, but continue to increase in the bone marrow and inflamed kidney. When LLPCs are depleted by the proteasome inhibitor bortezomib, their numbers regenerate within two weeks. Persistent depletion of LLPCs was achieved only by combining a cycle of bortezomib with maintenance therapy, for example cyclophosphamide, depleting the precursors of LLPCs or preventing their differentiation into LLPCs.

Conclusions

In SLE-prone NZB/W F1 mice, autoreactive LLPCs are generated throughout life. Their sustained therapeutic elimination requires both the depletion of LLPCs and the inhibition of their regeneration.

Autoantibodies from long-lived 'memory' plasma cells of NZB/W mice drive immune complex nephritis

OBJECTIVES

We have previously shown that both short- and long-lived plasma cells (PCs) significantly contribute to autoantibody production in NZB/W mice as a model of lupus nephritis. The aim of this study was to determine the role of autoreactive long-lived (memory) PCs refractory to immunosuppression and B cell depletion in the pathogenesis of systemic lupus erythematosus.

METHODS

Splenic CD138+ antibody-secreting cells (ASCs) from >6-month-old NZB/W mice with high titres of anti-dsDNA autoantibodies or from Balb/c mice 5 days after secondary immunisation with ovalbumin (OVA) were adoptively transferred to immunodeficient Rag1(-/-) mice, in which the development of nephritis was investigated by measuring proteinuria. Total IgG and IgM as well as anti-dsDNA and anti-OVA antibody levels were followed up by ELISA. After 21 weeks the recipient mice were sacrificed so that PCs in spleen and bone marrow could be analysed using ELISPOT and flow cytometry and renal immunohistology performed.

RESULTS

The adoptive transfer of NZB/W and anti-OVA ASCs resulted in the continuous generation of anti-dsDNA antibodies and anti-OVA antibodies, respectively, exclusively by long-lived PCs that had homed to the spleen and bone marrow of recipient Rag1(-/-) mice. Rag1(-/-) mice generating autoantibodies including anti-dsDNA had reduced survival, proteinuria and immune complex nephritis with C1q, C3, IgG and IgM deposits 21 weeks after transfer.

CONCLUSIONS

These findings demonstrate that autoantibodies exclusively secreted by long-lived (memory) PCs contribute to autoimmune pathology and should be considered as candidate targets for future therapeutic strategies.

Intraepidermal injection of dissociated epidermal cell suspension improves vitiligo

This study was initiated to evaluate the safety and effectiveness of intraepidermal injection of dissociated epidermal cells into the lesions of stable vitiligo patients. Autologous dissociated epidermal cell suspensions were injected intraepidermally into 10 stable vitiligo patients. None of the patients received adjuvant therapy. The response was evaluated as: marked (76-100%), moderate (51-75%), mild (26-50%) and minimal repigmentation (0-25%). Transmission electron microscopy was used to evaluate the transplanted cells and immunohistochemical staining with HMB-45 was performed to assess the repigmentation in vivo. In all cases, repigmentation started during the 4-week period after transplantation. Six months after transplantation, a marked repigmentation in four (40%), moderate repigmentation in two (20%) and mild repigmentation in two (20%) patients were observed. Two (20%) patients with white patches on their lids showed minimal repigmentation. No side effects were observed in any patients. Interestingly, repigmentation of gray hair in one patient, 4 months post transplantation was observed. Analysis of the ultrastructure of transplanted cells showed 1.5% of the cells had melanocyte morphology. HMB-45 positive cells were observed after cell transplantation. This method is an effective, simple and safe therapeutic option for stable vitiligo lesions.

Immunoglobulin Class (IgG, IgM) Determination by Dithiothreitol in Sensitized Kidney Transplant Candidates

Immunoglobulin class plays an important role in the histocompatibility crossmatch test to predict hyperacute rejection in kidney transplantation. The existing data indicates that immunoglobulin (Ig) M antibodies, particularly when they are autoantibodies, are not deleterious to the renal allograft. We used the reducing agent dithiotreitol (DTT) to inactivate IgM but not IgG in the crossmatch assay to help sensitized patients have the chance for successful transplantation. In this descriptive study, 57 candidates for kidney transplantation with final positive crossmatches who had a history of panel-reactive antibody (PRA) greater than 30% were selected. Two of 57 patients had systemic lupus erythematous (SLE). The sera of patients were treated by DTT and then measured for cytotoxicity against donor lymphocytes and a panel of 12 cells using the complement-dependent cytotoxicity (CDC) method. Autocrossmatch was also performed to differentiate autoantibodies and alloantibodies by the CDC method. Of the 57 patients, six subjects (10.53%) had IgM and 51 patients (89.47%) IgG in their serum against donor lymphocytes. Also against panel cells, 39 of 57 patients (68.43%) had IgG, three patients (5.26%) had IgM, and 15 patients (26.31%) had both IgG and IgM antibodies. Autolymphocytotoxic antibodies were detected in 1.75% patients (1 of 57) who had SLE. According to our results, 5.26% of the patients who were IgM-positive and IgG-negative for both crossmatch and PRA assays may experience successful kidney transplantation.