Impaired B Cell Apoptosis Results in Autoimmunity That Is Alleviated by Ablation of Btk.

While apoptosis plays a role in B-cell self-tolerance, its significance in preventing autoimmunity remains unclear. Here, we report that dysregulated B cell apoptosis leads to delayed onset autoimmune phenotype in mice. Our longitudinal studies revealed that mice with B cell-specific deletion of pro-apoptotic Bim ( ) have an expanded B cell compartment with a notable increase in transitional, antibody secreting and recently described double negative (DN) B cells.

Increased Risk of Ischemic Stroke in Systemic Sclerosis: A National Cohort Study of US Veterans.

Objective: Previously thought to involve primarily the microvasculature, systemic sclerosis (SSc) has been increasingly linked to macrovascular disease. Cardiovascular (CV) and cerebrovascular disease are responsible for 20-30% of mortality in SSc, but few studies have shown an independent association between SSc and stroke. We assessed whether SSc was an independent risk factor for ischemic stroke.

Conservation of pathogenic TCR homology across class II restrictions in anti-ribonucleoprotein autoimmunity: extended efficacy of T cell vaccine therapy.

T cells have been shown to mediate aspects of anti-ribonucleoprotein (RNP) autoimmunity, and are a potential target of therapy in lupus and related diseases. In this study, we assessed the relevance of a conserved class of anti-RNP T cells to autoimmune disease expression and therapy. Our data show that anti-RNP T cell selection induced a limited set of homologous CDR3 motifs at high frequency.

Ultraviolet radiation damages self noncoding RNA and is detected by TLR3.

Exposure to ultraviolet B (UVB) radiation from the sun can result in sunburn, premature aging and carcinogenesis, but the mechanism responsible for acute inflammation of the skin is not well understood. Here we show that RNA is released from keratinocytes after UVB exposure and that this stimulates production of the inflammatory cytokines tumor necrosis factor α (TNF-α) and interleukin-6 (IL-6) from nonirradiated keratinocytes and peripheral blood mononuclear cells (PBMCs). Whole-transcriptome sequencing revealed that UVB irradiation of keratinocytes induced alterations in the double-stranded domains of some noncoding RNAs.

T cell vaccination therapy in an induced model of anti-RNP autoimmune glomerulonephritis.

To establish the relevance of targeting disease-associated T cells in anti-RNP-associated glomerulonephritis, mice developing nephritis following immunization with U1-70-kd small nuclear ribonucleoprotein (snRNP) were treated with a single dose of irradiated antigen-selected T cell vaccine. T cell receptor usage in nephritic kidneys revealed oligoclonal use of T Cell Receptor V Beta (TRBV) genes as previously found in spleens and lungs of immunized mice with pulmonary disease. The CDR3 regions from T cell isolates showed sequence homology to those in humans with anti-RNP autoimmunity.

Endosomal Toll-like receptors in autoimmunity: mechanisms for clinical diversity.

The endosomal Toll-like receptors (TLR3, TLR7 and TLR9) have been implicated in the pathogenesis of autoimmune diseases. Their signaling pathways show remarkable similarities and yet the outcomes following activation of each of these TLRs lead to clinically distinct autoimmune disease phenotypes. This review discusses how differences may arise at a molecular and cellular level to account for this diversity of responses.

Recent advances and opportunities in research on lupus: environmental influences and mechanisms of disease.

We summarize research on mechanisms through which environmental agents may affect the pathogenesis of lupus, discuss three exposures that have been the focus of research in this area, and propose recommendations for new research initiatives. We examined studies pertaining to key mechanistic events and specific exposures. Apoptosis leading to increased production or decreased clearance of immunogenic intracellular self-antigens and defective apoptosis of autoreactive immune cells both have been implicated in the loss of self-tolerance.

Tissue targeting of anti-RNP autoimmunity: effects of T cells and myeloid dendritic cells in a murine model.

Objective: To explore the role of immune cells in anti-RNP autoimmunity in a murine model of pneumonitis or glomerulonephritis, using adoptive transfer techniques.

Methods: Donor mice were immunized with 50 mug of U1-70-kd small nuclear RNP fusion protein and 50 mug of U1 RNA adjuvant. Whole splenocytes as well as CD4+ cell and dendritic cell (DC) subsets from the immunized mice were infused into naive syngeneic recipients.

Recent advances and opportunities in research on lupus: environmental influences and mechanisms of disease.

Objectives: In this review we summarize research on mechanisms through which environmental agents may affect the pathogenesis of lupus, discuss three exposures that have been the focus of research in this area, and propose recommendations for new research initiatives.

Data Sources And Synthesis: We examined studies pertaining to key mechanistic events and specific exposures. Apoptosis leading to increased production or decreased clearance of immunogenic intracellular self-antigens and defective apoptosis of autoreactive immune cells both have been implicated in the loss of self-tolerance.

CD4+ T cells target epitopes residing within the RNA-binding domain of the U1-70-kDa small nuclear ribonucleoprotein autoantigen and have restricted TCR diversity in an HLA-DR4-transgenic murine model of mixed connective tissue disease.

Mixed connective tissue disease (MCTD) is a systemic autoimmune disease with significant morbidity and premature mortality of unknown pathogenesis. In the present study, we characterized U1-70-kDa small nuclear ribonucleoprotein (70-kDa) autoantigen-specific T cells in a new murine model of MCTD. These studies defined 70-kDa-reactive T cell Ag fine specificities and TCR gene usage in this model.

Clinical and immunologic manifestations of mixed connective tissue disease in a Miami population compared to a Midwestern US Caucasian population.

Objective: A cross-sectional study of mixed connective tissue disease (MCTD) was performed to determine if there were identifiable differences in the clinical expression of MCTD associated with race or ethnicity.

Methods: Miami, Florida, and Midwestern US (Missouri) Caucasian MCTD cohorts were studied. Clinical and laboratory features of the 2 MCTD cohorts were compared.

Differential tissue targeting of autoimmunity manifestations by autoantigen-associated Y RNAs.

Objective: To assess the Y RNAs, a family of homologous RNAs that bind to the Ro autoantigen, for the ability to contribute to autoimmune disease by activating RNA-responsive Toll-like receptors (TLRs).

Methods: Using cell lines expressing or stably transfected with TLR-3, TLR-7, or TLR-8, we determined the patterns of RNA-specific TLR activation by in vitro transcripts of all of the known murine and human Y RNAs. Next, 8-10-week-old female mice were exposed to a single 50-microg subcutaneous injection of mouse Y1 or mouse Y3 RNA, and the effects were observed.

Anti-ribonucleoprotein antibodies mediate enhanced lung injury following mesenteric ischemia/reperfusion in Rag-1(-/-) mice.

Natural Abs and autoantibodies bind antigens displayed by ischemia-conditioned tissues, followed by complement activation and enhanced tissue injury during reperfusion. Anti-ribonucleoprotein (RNP) Ab is associated with lung disease in patients with autoimmune disease but it is not known whether these abs contribute to lung injury. Mesenteric I/R in mice leads to local and remote lung injury.

A murine model of mixed connective tissue disease induced with U1 small nuclear RNP autoantigen.

Objective: To test whether immunizing mice with autoantigens closely linked to mixed connective tissue disease (MCTD) could induce an MCTD-like clinical syndrome distinguishable from systemic lupus erythematosus (SLE).

Methods: Transgenic and knockout C57BL/6-derived mice were immunized subcutaneously at age 8-12 weeks with U1-70-kd small nuclear RNP (70K) fusion protein along with either Freund's complete adjuvant (CFA) or U1 RNA. After 2 months, mice were killed and analyzed histologically and serologically.

Autoantibodies in the pathogenesis of mixed connective tissue disease.

Antibodies to U1-RNP are part of the clinical definition of mixed connective tissue disease (MCTD). These antibodies and other well-defined antibodies tend to arise together in affected patients. Although still speculative, hypotheses that link U1-RNP antibodies to the development of autoimmunity in MCTD and that associate U1-RNP antibodies with mechanisms of tissue injury in MCTD have emerged and are being tested.

Patients with antibodies to both PmScl and dsDNA.

Objective: To determine the significance of dsDNA antibodies in patients with antibodies to PmScl.

Methods: All patients testing positive for PmScl and/or dsDNA antibodies at an academic medical center between 1977 and 2002 were identified. Charts for the PmScl-positive patients were reviewed for manifestations of lupus, scleroderma, or polymyositis/dermatomyositis.

U1 RNA induces innate immunity signaling.

Objective: The U1-70-kd RNP is a prominent target of autoimmunity in connective tissue diseases. In this study, we explored whether its endogenous ligand, U1 RNA, mediates a proimmune signal and may be immunogenic.

Methods: We assayed the proliferation of control and MyD88-knockout splenocytes in response to in vitro-synthesized U1 RNA, and measured interleukin-6 (IL-6) and IL-8 secretion induced by U1 RNA in a human cell line competent for signaling through Toll-like receptor 3 (TLR-3) and TLR-5.

Human T cell clones specific for heterogeneous nuclear ribonucleoprotein A2 autoantigen from connective tissue disease patients assist in autoantibody production.

Objective: To identify and characterize human T cells reactive with heterogeneous nuclear RNP A2 (hnRNP A2) antigen, and to determine the ability of hnRNP-reactive T cells to assist in the production of human autoantibodies.

Methods: T cells from patients with high serum levels of anti-hnRNP IgG autoantibody were stimulated with an hnRNP recombinant fusion protein, and the cells were cloned by limiting dilution. The surface phenotype and cytokine profiles of the T cells were examined by flow cytometry and enzyme-linked immunosorbent assay (ELISA), respectively.

Cloned human TCR from patients with autoimmune disease can respond to two structurally distinct autoantigens.

There is increasing evidence that the TCR can have significant plasticity in the range of Ags that a single receptor can recognize. Although it has been proposed that such TCR plasticity might contribute to autoimmunity, there have been few studies examining this possibility in either animal models or human disease. In the present study, we examined human T cell clones that were generated against two structurally dissimilar proteins, U1-70 kDa and Smith-B, that are physically associated in the U1-small nuclear ribonucleoprotein complex and that are frequent targets of autoantibodies and T cells in the same lupus patient.

A major B cell epitope present on the apoptotic but not the intact form of the U1-70-kDa ribonucleoprotein autoantigen.

Apoptotically modified forms of autoantigens have been hypothesized to participate in lupus immunopathogenesis. This study identifies a major B cell epitope present on the apoptotic but not the intact form of the U1-70-kDa ribonucleoprotein lupus autoantigen (70k). Human autoimmune sera with strong recognition of apoptotic 70k and minimal recognition of intact 70k were identified and tested for reactivity to truncated forms of 70k by immunoblot and ELISA.

Lack of autoantibody production associated with cytomegalovirus infection.

To confirm an association between cytomegalovirus (CMV) infection and the presence of antibodies to Smith (Sm), to ribonucleoprotein (RNP), and to a component of the U1 ribonucleoproteins (U1-70 kD), we measured antibodies to these protein antigens using an enzyme immunoassay and an immunoblot. The antibodies were measured in the sera of 80 healthy subjects, one-half of whom were naturally CMV seropositive and one-half were CMV seronegative, and in eight subjects immunized with a live attenuated strain of CMV. None of the vaccinees developed antibodies to Sm, to RNP, or to U1-70 kD at either 4 or 12 months after immunization.

T cell immunity in connective tissue disease patients targets the RNA binding domain of the U1-70kDa small nuclear ribonucleoprotein.

Although the T cell dependence of autoimmune responses in connective tissue diseases has been well established, limited information exists regarding the T cell targeting of self Ags in humans. To characterize the T cell response to a connective tissue disease-associated autoantigen, this study generated T cell clones from patients using a set of peptides encompassing the entire linear sequence of the 70-kDa subunit of U1 snRNP (U1-70kDa) small nuclear ribonucleoprotein. Despite the ability of U1-70kDa to undergo multiple forms of Ag modification that have been correlated with distinct clinical disease phenotypes, a remarkably limited and consistent pattern of T cell targeting of U1-70kDa was observed.

Apoptotic U1-70 kd is antigenically distinct from the intact form of the U1-70-kd molecule.

Objective: To determine whether immune responses to an apoptotically modified form of a human lupus autoantigen can be distinguished from immune responses to the intact form of the same antigen.

Methods: Immunoblot and enzyme-linked immunosorbent assay techniques were used to test human autoimmune sera for the presence of antibodies to apoptotic forms of the U1- 70-kd small nuclear RNP antigen, while antibody recognition of intact U1-70 kd was blocked.

Results: poptosis-specific U1-70-kd antibodies were identified by immunoblot in 15 of 29 sera with antibodies to intact U1-70 kd and in 2 of 25 sera without measurable antibodies to intact U1-70 kd.