Spontaneous class switching and B cell hyperactivity increase autoimmunity against intracellular self antigen in Lyn-deficient mice

Multi-omics study reveals different pathogenesis of the generation of skin lesions in SLE and IDLE patients

Lupus erythematosus (LE) is a heterogeneous, antibody-mediated autoimmune disease. Isolate discoid LE (IDLE) and systematic LE (SLE) are traditionally regarded as the two ends of the spectrum, ranging from skin-limited damage to life-threatening multi-organ involvement. Both belong to LE, but IDLE and SLE differ in appearance of skin lesions, autoantibody panels, pathological changes, treatments, and immunopathogenesis. Is discoid lupus truly a form of LE or is it a completely separate entity? This question has not been fully elucidated. We compared the clinical data of IDLE and SLE from our center, applied multi-omics technology, such as immune repertoire sequencing, high-resolution HLA alleles sequencing and multi-spectrum pathological system to explore cellular and molecular phenotypes in skin and peripheral blood from LE patients. Based on the data from 136 LE patients from 8 hospitals in China, we observed higher damage scores and fewer LE specific autoantibodies in IDLE than SLE patients, more uCDR3 sharing between PBMCs and skin lesion from SLE than IDLE patients, elevated diversity of V-J recombination in IDLE skin lesion and SLE PBMCs, increased SHM frequency and class switch ratio in IDLE skin lesion, decreased SHM frequency but increased class switch ratio in SLE PBMCs, HLA-DRB1*03:01:01:01, HLA-B*58:01:01:01, HLA-C*03:02:02:01, and HLA-DQB1*02:01:01:01 positively associated with SLE patients, and expanded Tfh-like cells with ectopic germinal center structures in IDLE skin lesions. These findings suggest a significant difference in the immunopathogenesis of skin lesions between SLE and IDLE patients. SLE is a B cell-predominate systemic immune disorder, while IDLE appears limited to the skin. Our findings provide novel insights into the pathogenesis of IDLE and other types of LE, which may direct more accurate diagnosis and novel therapeutic strategies.

Systems level analysis of systemic sclerosis shows a network of immune and profibrotic pathways connected with genetic polymorphisms

Systemic sclerosis (SSc) is a rare systemic autoimmune disease characterized by skin and organ fibrosis. The pathogenesis of SSc and its progression are poorly understood. The SSc intrinsic gene expression subsets (inflammatory, fibroproliferative, normal-like, and limited) are observed in multiple clinical cohorts of patients with SSc. Analysis of longitudinal skin biopsies suggests that a patient's subset assignment is stable over 6-12 months. Genetically, SSc is multi-factorial with many genetic risk loci for SSc generally and for specific clinical manifestations. Here we identify the genes consistently associated with the intrinsic subsets across three independent cohorts, show the relationship between these genes using a gene-gene interaction network, and place the genetic risk loci in the context of the intrinsic subsets. To identify gene expression modules common to three independent datasets from three different clinical centers, we developed a consensus clustering procedure based on mutual information of partitions, an information theory concept, and performed a meta-analysis of these genome-wide gene expression datasets. We created a gene-gene interaction network of the conserved molecular features across the intrinsic subsets and analyzed their connections with SSc-associated genetic polymorphisms. The network is composed of distinct, but interconnected, components related to interferon activation, M2 macrophages, adaptive immunity, extracellular matrix remodeling, and cell proliferation. The network shows extensive connections between the inflammatory- and fibroproliferative-specific genes. The network also shows connections between these subset-specific genes and 30 SSc-associated polymorphic genes including STAT4, BLK, IRF7, NOTCH4, PLAUR, CSK, IRAK1, and several human leukocyte antigen (HLA) genes. Our analyses suggest that the gene expression changes underlying the SSc subsets may be long-lived, but mechanistically interconnected and related to a patients underlying genetic risk.

CD22 and autoimmune disease

CD22 is a 140-kDa member of the Siglec family of cell surface proteins that is expressed by most mature B-cell lineages. As a co-receptor of the B-cell receptor (BCR), it is known to contribute to the sensitive control of the B-cell response to antigen. Cross-linking of CD22 and the BCR by antigen triggers the phosphorylation of CD22, which leads to activation of signaling molecules such as phosphatases. Signal transduction pathways involving CD22 have been explored in a number of mouse models, some of which have provided evidence that in the absence of functional CD22, B cells have a "hyperactivated" phenotype, and suggest that loss of CD22 function could contribute to the pathogenesis of autoimmune diseases. Modulating CD22 activity has therefore been suggested as a possible therapeutic approach to such diseases. For example, the novel CD22-targeting monoclonal antibody epratuzumab is currently under investigation as a treatment for the connective tissue disorder systemic lupus erythematosus (SLE).

Reporting the Implementation of the Three Rs in European Primate and Mouse Research Papers: Are We Making Progress?

It is now more than 20 years since both Council of Europe Convention ETS123 and EU Directive 86/609?EEC were introduced, to promote the implementation of the Three Rs in animal experimentation and to provide guidance on animal housing and care. It might therefore be expected that reports of the implementation of the Three Rs in animal research papers would have increased during this period. In order to test this hypothesis, a literature survey of animal-based research was conducted. A randomly-selected sample from 16 high-profile medical journals, of original research papers arising from European institutions that featured experiments which involved either mice or primates, were identified for the years 1986 and 2006 (Total sample = 250 papers). Each paper was scored out of 10 for the incidence of reporting on the implementation of Three Rs-related factors corresponding to Replacement (justification of non-use of non-animal methods), Reduction (statistical analysis of the number of animals needed) and Refinement (housing aspects, i.e. increased cage size, social housing, enrichment of cage environment and food; and procedural aspects, i.e. the use of anaesthesia, analgesia, humane endpoints, and training for procedures with positive reinforcement). There was no significant increase in overall reporting score over time, for either mouse or primate research. By 2006, mouse research papers scored an average of 0 out of a possible 10, and primate research papers scored an average of 1.5. This review provides systematic evidence that animal research is still not properly reported, and supports the call within the scientific community for action to be taken by journals to update their policies.

CD22: an inhibitory enigma

CD22 is an inhibitory coreceptor of the B-cell receptor (BCR), and plays a critical role in establishing signalling thresholds for B-cell activation. Like other coreceptors, the ability of CD22 to modulate B-cell signalling is critically dependent upon its proximity to the BCR, and this in turn is governed by the binding of its extracellular domain to alpha2,6-linked sialic acid ligands. Manipulation of CD22 ligand binding in various experimental settings has profound effects on B-cell signalling, but as yet there is no complete model for how ligand binding in vivo controls normal CD22 function. Several elegant studies have recently shed light on this issue, although the results appear to suggest two mutually exclusive models for the role of ligand binding; in either promoting or inhibiting, CD22 function. We shall therefore discuss these results in detail, and suggest possible approaches by which these conflicting experimental findings might be reconciled. We shall also consider a second important issue in CD22 biology, which relates to the role that defects in this receptor might play in mediating autoimmune disease. We review the current evidence for this, and discuss the importance of genetic background in modifying CD22 function and predisposition to autoimmunity.

MyD88-dependent autoimmune disease in Lyn-deficient mice

Recent evidence suggests that systemic autoimmune disease depends on signals from TLR ligands, but little is known about how TLR-dependent pathways lead to the loss of self tolerance in vivo. To address this, we have examined the role of TLR signaling in Lyn-deficient mice, which develop an autoimmune disease similar to SLE. We found that absence of the TLR signaling adaptor molecule MyD88 suppresses plasma cell differentiation of switched and unswitched B cells, and prevents the generation of antinuclear IgG antibodies and glomerulonephritis. In mixed chimeras the increased IgM and IgG antibody secretion in Lyn-deficient mice is at least partially due to B cell-independent effects of Lyn. We now show that MyD88 deficiency blocks the expansion and activation of DC in which Lyn is also normally expressed, and prevents the hypersecretion of proinflammatory cytokines IL-6 and IL-12 by Lyn-deficient DC. These findings further highlight the important role of TLR-dependent signals in both lymphocyte activation and autoimmune pathogenesis.