Differential activation of anti-erythrocyte and anti-DNA autoreactive B lymphocytes by the Yaa mutation

An as-yet-unidentified mutation, Y-linked autoimmune acceleration (Yaa), is responsible for the accelerated development of lupus-like autoimmune syndrome in mice. In view of a possible role for Yaa as a positive regulator of BCR signaling, we have explored whether the expression of the Yaa mutation affects the development and activation of transgenic autoreactive B cells expressing either 4C8 IgM anti-RBC or Sp6 IgM anti-DNA. In this study, we show that the expression of the Yaa mutation induced a lethal form of autoimmune hemolytic anemia in 4C8 transgenic C57BL/6 mice, likely as a result of activation of 4C8 anti-RBC autoreactive B cells early in life. This was further supported, although indirectly, by increased T cell-independent IgM production in spleens of nontransgenic C57BL/6 mice bearing the Yaa mutation. In contrast, Yaa failed to induce activation of Sp6 anti-DNA autoreactive B cells, consistent with a lack of increased IgM anti-DNA production in nontransgenic C57BL/6 Yaa mice. Our results suggest that Yaa can activate autoreactive B cells in a BCR-dependent manner, related to differences in the form and nature of autoantigens

Membrane-Bound TNF Induces Protective Immune Responses to M. bovis BCG Infection: Regulation of memTNF and TNF Receptors Comparing Two memTNF Molecules

Several activities of the transmembrane form of TNF (memTNF) in immune responses to intracellular bacterial infection have been shown to be different from those exerted by soluble TNF. Evidence is based largely on studies in transgenic mice expressing memTNF, but precise cellular mechanisms are not well defined and the importance of TNF receptor regulation is unknown. In addition, memTNF activities are defined for a particular modification of the extracellular domain of TNF but a direct comparison of different mutant memTNF molecules has not been done in vivo

Selective APRIL Blockade Delays Systemic Lupus Erythematosus in Mouse

SLE pathogenesis is complex, but it is now widely accepted that autoantibodies play a key role in the process by forming excessive immune complexes; their deposits within tissues leading to inflammation and functional damages. A proliferation inducing ligand (APRIL) is a member of the tumor necrosis factor (TNF) superfamily mediating antibody-producing plasma cell (PC)-survival that may be involved in the duration of pathogenic autoantibodies in lupus. We found significant increases of APRIL at the mRNA and protein levels in bone marrow but not spleen cells from NZB/W lupus mice, as compared to control mice. Selective antibody-mediated APRIL blockade delays disease development in this model by preventing proteinuria, kidney lesions, and mortality. Notably, this was achieved by decreasing anti-DNA and anti-chromatin autoantibody levels, without any perturbation of B- and T- cell homeostasis. Thus, anti-APRIL treatment may constitute an alternative therapy in SLE highly specific to PCs compared to other B-cell targeting therapies tested in this disease, and likely to be associated with less adverse effects than any anti-inflammatory and immunosuppressant agents previously used

TLR Tolerance Reduces IFN-Alpha Production Despite Plasmacytoid Dendritic Cell Expansion and Anti-Nuclear Antibodies in NZB Bicongenic Mice

Genetic loci on New Zealand Black (NZB) chromosomes 1 and 13 play a significant role in the development of lupus-like autoimmune disease. We have previously shown that C57BL/6 (B6) congenic mice with homozygous NZB chromosome 1 (B6.NZBc1) or 13 (B6.NZBc13) intervals develop anti-nuclear antibodies and mild glomerulonephritis (GN), together with increased T and B cell activation. Here, we produced B6.NZBc1c13 bicongenic mice with both intervals, and demonstrate several novel phenotypes including: marked plasmacytoid and myeloid dendritic cell expansion, and elevated IgA production. Despite these changes, only minor increases in anti-nuclear antibody production were seen, and the severity of GN was reduced as compared to B6.NZBc1 mice. Although bicongenic mice had increased levels of baff and tnf-α mRNA in their spleens, the levels of IFN-α-induced gene expression were reduced. Splenocytes from bicongenic mice also demonstrated reduced secretion of IFN-α following TLR stimulation in vitro. This reduction was not due to inhibition by TNF-α and IL-10, or regulation by other cellular populations. Because pDC in bicongenic mice are chronically exposed to nuclear antigen-containing immune complexes in vivo, we examined whether repeated stimulation of mouse pDC with TLR ligands leads to impaired IFN-α production, a phenomenon termed TLR tolerance. Bone marrow pDC from both B6 and bicongenic mice demonstrated markedly inhibited secretion of IFN-α following repeated stimulation with a TLR9 ligand. Our findings suggest that the expansion of pDC and production of anti-nuclear antibodies need not be associated with increased IFN-α production and severe kidney disease, revealing additional complexity in the regulation of autoimmunity in systemic lupus erythematosus

Pathway of Toll-Like Receptor 7/B Cell Activating Factor/B Cell Activating Factor Receptor Plays a Role in Immune Thrombocytopenia In Vivo

Immune thrombocytopenia (ITP) is an autoimmune disorder characterized by anti-platelet autoantibody-mediated platelet destruction. Antigen-presenting cell (APC) dysfunction is considered to play crucial roles in ITP. However, how APC affects autoreactive B cells in ITP is still unknown. Using a mouse model of immune thrombocytopenia, we demonstrated an increase in levels of TLR7 in splenic mononuclear cells (SMCs). Using both TLR7 agonist and TLR7 silencing lentivirus, we found stimulation of TLR7 decreased platelet counts and increased levels of platelet-associated IgG (PAIgG) in ITP mice, which correlates TLR7 with platelet destruction by autoantibodies. Levels of serum BAFF increased significantly in ITP mice and stimulation of TLR7 promoted secretion of BAFF. Among the three BAFF receptors, only BAFF receptor (BAFF-R) increased in ITP mice. However, activation of TLR7 showed no effect on the expression of BAFF receptors. These findings indicate that upregulation of TLR7 may augment BAFF secretion by APC and through ligation of BAFF-R promote autoreactive B cell survival and thus anti-platelet autoantibody production. The pathway of TLR7/BAFF/BAFF-R provides us with an explanation of how activation of APC affects autoantibody production by B cells in ITP and thus might provide a reasonable therapeutic strategy for ITP

Mutually Positive Regulatory Feedback Loop between Interferons and Estrogen Receptor-α in Mice: Implications for Sex Bias in Autoimmunity

gene) and stimulates expression of target genes. female mice had relatively higher steady-state levels of mRNAs encoded by the IFN and ERα-responsive genes as compared to the age-matched males.Our observations identify a novel mutually positive regulatory feedback loop between IFNs and ERα in immune cells in mice and support the idea that activation of this regulatory loop contributes to sex bias in SLE

Type I IFN and TNFα cross-regulation in immune-mediated inflammatory disease: basic concepts and clinical relevance

A cross-regulation between type I IFN and TNFα has been proposed recently, where both cytokines are hypothesized to counteract each other. According to this model, different autoimmune diseases can be viewed as disequilibrium between both cytokines. As this model may have important clinical implications, the present review summarizes and discusses the currently available clinical evidence arguing for or against the proposed cross-regulation between TNFα and type I IFN. In addition, we review how this cross-regulation works at the cellular and molecular levels. Finally, we discuss the clinical relevance of this proposed cross-regulation for biological therapies such as type I IFN or anti-TNFα treatment

Interleukin 6 Accelerates Mortality by Promoting the Progression of the Systemic Lupus Erythematosus-Like Disease of BXSB. Yaa Mice

IL6 is a multifunctional cytokine that drives terminal B cell differentiation and secretion of immunoglobulins. IL6 also cooperates with IL21 to promote differentiation of CD4(+) T follicular helper cells (TFH). Elevated serum levels of IL6 correlate with disease flares in patients with systemic lupus erythematosus (SLE). We previously reported that IL21 produced by T-FH plays a critical role in the development of the SLE-like disease of BXSB. Yaa mice. To examine the possible contributions of IL6 to disease, we compared disease parameters in IL6-deficient and IL6-competent BXSB. Yaa mice. We report that survival of IL6-deficient BXSB. Yaa mice was significantly prolonged in association with significant reductions in a variety of autoimmune manifestations. Moreover, B cells stimulated by co-engagement of TLR7 and B cell receptor (BCR) produced high levels of IL6 that was further augmented by stimulation with Type I interferon (IFN1). Importantly, the frequencies of T-FH and serum levels of IL21 were significantly reduced in IL6-deficient mice. These findings suggest that high-level production of IL6 by B cells induced by integrated signaling from the IFN1 receptor, TLR7 and BCR promotes the differentiation of IL21-secreting T-FH in a signaling sequence that drives the lethal autoimmune disease of BXSB. Yaa mice.Peer reviewe

Selective blockade of interferon-α and -β reveals their non-redundant functions in a mouse model of West Nile virus infection

Although type I interferons (IFNs) were first described almost 60 years ago, the ability to monitor and modulate the functional activities of the individual IFN subtypes that comprise this family has been hindered by a lack of reagents. The major type I IFNs, IFN-β and the multiple subtypes of IFN-α, are expressed widely and induce their effects on cells by interacting with a shared heterodimeric receptor (IFNAR). In the mouse, the physiologic actions of IFN-α and IFN-β have been defined using polyclonal anti-type I IFN sera, by targeting IFNAR using monoclonal antibodies or knockout mice, or using Ifnb-/- mice. However, the corresponding analysis of IFN-α has been difficult because of its polygenic nature. Herein, we describe two monoclonal antibodies (mAbs) that differentially neutralize murine IFN-β or multiple subtypes of murine IFN-α. Using these mAbs, we distinguish specific contributions of IFN-β versus IFN-α in restricting viral pathogenesis and identify IFN-α as the key mediator of the antiviral response in mice infected with West Nile virus. This study thus suggests the utility of these new reagents in dissecting the antiviral and immunomodulatory roles of IFN-β versus IFN-α in murine models of infection, immunity, and autoimmunity