Recovery from autoimmunity of MRL/lpr mice after infection with an interleukin-2/vaccinia recombinant virus

Interleukin-2 (IL-2) is a T-cell derived molecule implicated in the clonal expansion of antigen-activated T cells and in T-cell development. IL-2 is also implicated in autoimmune disease, although its role is still controversial. Murine systemic lupus erythematosus (SLE) is a good model for human SLE as most of the immunological abnormalities in the human disease also seem to be operative in the mouse. Among SLE mice, the MRL/lpr strain develops early in life autoimmune diseases such as immune complex-mediated glomerulonephritis, arthritis and arteritis. Lymphoid abnormalities associated with those diseases in this strain are thymic atrophy and abnormal proliferation of CD3+ CD4- CD8- 'double-negative' T cells, resulting in massive generalized lymph node enlargement. We have therefore now examined the effects of IL-2 on the disease progression in MRL/lpr mice using live vaccinia recombinant viruses expressing the human IL-2 gene. Vaccinated mice showed prolonged survival, decreased autoantibody and rheumatoid factor titres, marked attenuation of kidney interstitial infiltration and intraglomerular proliferation, as well as clearance of synovial mononuclear infiltrates. Inoculation with the IL-2/vaccinia recombinant virus led, in addition, to drastic reduction of the double-negative T-cell population, improved thymic differentiation and restoration of normal values of mature cells in peripheral lymphoid organs.     

Antigen-induced apoptotic death of Ly-1 B cells responsible for autoimmune disease in transgenic mice.

Studies on transgenic mice expressing immunoglobulins against self-antigens have shown that self-tolerance is maintained by active elimination (clonal deletion), functional inactivation (clonal anergy) of self-reactive B cells, or a combination of both. We have established and characterized a transgenic mouse line expressing an anti-erythrocyte autoantibody. In contrast to other autoantibody transgenic lines, about 50% of the animals of this transgenic line suffer from autoimmune disease, indicating a loss of self-tolerance. Here we show that peritoneal Ly-1 B cells (also known as B-1 cells) are responsible for this autoimmune disease in our transgenic mice. A few self-reactive Ly-1 B cells that have somehow escaped the deletion mechanism expand in the peritoneum because of the absence of self-antigen. These Ly-1 B cells are eliminated in vivo by apoptosis once exposed to self-antigen. On the basis of these results we propose a novel autoantibody production mechanism whereby self-reactive B cells sequestered in compartments free of self-antigens may survive, proliferate and be activated for generation of pathogenic autoantibodies in autoimmune diseases.     

ICOS co-stimulatory receptor is essential for T-cell activation and function

T-lymphocyte activation and immune function are regulated by co-stimulatory molecules. CD28, a receptor for B7 gene products, has a chief role in initiating T-cell immune responses. CTLA4, which binds B7 with a higher affinity, is induced after T-cell activation and is involved in downregulating T-cell responses. The inducible co-stimulatory molecule (ICOS), a third member of the CD28/CTLA4 family, is expressed on activated T cells. Its ligand B7H/B7RP-1 is expressed on B cells and in non-immune tissues after injection of lipopolysaccharide into animals. To understand the role of ICOS in T-cell activation and function, we generated and analysed ICOS-deficient mice. Here we show that T-cell activation and proliferation are defective in the absence of ICOS. In addition, ICOS -/- T cells fail to produce interleukin-4 when differentiated in vitro or when primed in vivo. ICOS is required for humoral immune responses after immunization with several antigens. ICOS-/- mice showed greatly enhanced susceptibility to experimental autoimmune encephalomyelitis, indicating that ICOS has a protective role in inflammatory autoimmune diseases.     

Breakdown of self-tolerance in anergic B lymphocytes.

Production of autoantibodies, which characterizes most autoimmune diseases, is normally avoided by active elimination or functional inactivation (anergy) of B and T lymphocytes bearing receptors for self antigens. The mechanisms leading to the escape of self-reactive clones from these normal tolerance mechanisms in autoimmune diseases nevertheless remain obscure. Here, we demonstrate that clonal anergy in B lymphocytes is a reversible process, and that silenced self-reactive B cells can be reactivated under particular conditions to give rise to vigorous antibody responses. Reactivation of anergic lymphocytes may explain many examples of transient autoimmune reactions in normal individuals, and may under pathological conditions be important in the development of chronic autoimmune disease.     

Infection breaks T-cell tolerance.

Clonal deletion or clonal anergy establish tolerance in T cells that bear potentially autoreactive antigen receptors. Here we report that concomitant infection with the nematode Nippostrongylus brasiliensis breaks an established T-cell tolerance induced by injection of mice with Staphylococcus enterotoxin B (SEB). CD4+ T cells from SEB-tolerant mice did not produce either interleukin-2 or interleukin-4 when challenged in vitro with SEB. N. brasiliensis infection of SEB-primed animals resulted in a normal expansion of SEB-tolerant CD4+V beta 8+ T cells in vivo as well as an equivalent increase of SEB-reactive, interleukin-4-producing CD4+V beta 8+ T cells both in SEB-tolerant and in normal animals. Thus, infection with N. brasiliensis circumvented the tolerance established with SEB. Activation of anergic, potentially autoreactive CD4+ T cells by infectious agents seems to be a major pathway for the initiation of autoimmune diseases. Our results suggest that infectious agents may break tolerance in potentially autoreactive CD4+ T cells by activation of alternative reaction pathways.     

Regulation of B-cell survival by BAFF-dependent PKCdelta-mediated nuclear signalling

Approximately 65% of B cells generated in human bone marrow are potentially harmful autoreactive B cells. Most of these cells are clonally deleted in the bone marrow, while those autoreactive B cells that escape to the periphery are anergized or perish before becoming mature B cells. Escape of self-reactive B cells from tolerance permits production of pathogenic auto-antibodies; recent studies suggest that extended B lymphocyte survival is a cause of autoimmune disease in mice and humans. Here we report a mechanism for the regulation of peripheral B-cell survival by serine/threonine protein kinase Cdelta (PKCdelta): spontaneous death of resting B cells is regulated by nuclear localization of PKCdelta that contributes to phosphorylation of histone H2B at serine 14 (S14-H2B). We show that treatment of B cells with the potent B-cell survival factor BAFF ('B-cell-activating factor belonging to the TNF family') prevents nuclear accumulation of PKCdelta. Our data suggest the existence of a previously unknown BAFF-induced and PKCdelta-mediated nuclear signalling pathway which regulates B-cell survival.     

Th1-specific cell surface protein Tim-3 regulates macrophage activation and severity of an autoimmune disease

Activation of naive CD4(+) T-helper cells results in the development of at least two distinct effector populations, Th1 and Th2 cells. Th1 cells produce cytokines (interferon (IFN)-gamma, interleukin (IL)-2, tumour-necrosis factor (TNF)-alpha and lymphotoxin) that are commonly associated with cell-mediated immune responses against intracellular pathogens, delayed-type hypersensitivity reactions, and induction of organ-specific autoimmune diseases. Th2 cells produce cytokines (IL-4, IL-10 and IL-13) that are crucial for control of extracellular helminthic infections and promote atopic and allergic diseases. Although much is known about the functions of these two subsets of T-helper cells, there are few known surface molecules that distinguish between them. We report here the identification and characterization of a transmembrane protein, Tim-3, which contains an immunoglobulin and a mucin-like domain and is expressed on differentiated Th1 cells. In vivo administration of antibody to Tim-3 enhances the clinical and pathological severity of experimental autoimmune encephalomyelitis (EAE), a Th1-dependent autoimmune disease, and increases the number and activation level of macrophages. Tim-3 may have an important role in the induction of autoimmune diseases by regulating macrophage activation and/or function.     

rhsBLyS活性检测方法的比较

以FluroBeads B荧光磁珠法体外分离并培养人B淋巴细胞作为研究材料，通过MTT法、^3H-TdR掺入法测定重组入B淋巴细胞刺激因子(rhsBLyS)对人B淋巴细胞的促增殖活性并进行相应比较．结果表明：rhsBLyS非融合蛋白在引发剂Anti-IgM的协同作用下表现出显著刺激B淋巴细胞增殖的活性，且两种方法所得结果一致，充分验证了rhsBLyS样品的活性；MTT法检测可替代放射性同位素法．     

Class IV semaphorin Sema4A enhances T-cell activation and interacts with Tim-2

Semaphorins are a family of phylogenetically conserved soluble and transmembrane proteins. Although many soluble semaphorins deliver guidance cues to migrating axons during neuronal development, some members are involved in immune responses. For example, CD100 (also known as Sema4D), a class IV transmembrane semaphorin, signals through CD72 to effect nonredundant roles in immune responses in a ligand-receptor system that is distinct from any seen previously in the nervous system. Here we report that the class IV semaphorin Sema4A, which is expressed in dendritic cells and B cells, enhances the in vitro activation and differentiation of T cells and the in vivo generation of antigen-specific T cells. Treating mice with monoclonal antibodies against Sema4A blocks the development of an experimental autoimmune encephalomyelitis that is induced by an antigenic peptide derived from myelin oligodendrocyte glycoprotein. In addition, expression cloning shows that the Sema4A receptor is Tim-2, a member of the family of T-cell immunoglobulin domain and mucin domain (Tim) proteins that is expressed on activated T cells.     

SLE患者TNF B—2等位基因频率分析

目的 检测系统性红斑狼疮（SLE）患者肿瘤坏死因子（TNF B－2）等位基因频率,寻找SLE的易感基因。方法 采用聚合酶链式反应－限制性片段长度多态性（PCR－RFLP）分析法。结果 SLE患者TNF B－2等位基因频率比正常显著增高（P＜0．01）。结论 TNF B－2等位基因可能是SLE的易感基因或易感基因的标记基因。     

Non-apoptotic role of BID in inflammation and innate immunity

Innate immunity is a fundamental defence response that depends on evolutionarily conserved pattern recognition receptors for sensing infections or danger signals. Nucleotide-binding and oligomerization domain (NOD) proteins are cytosolic pattern-recognition receptors of paramount importance in the intestine, and their dysregulation is associated with inflammatory bowel disease. They sense peptidoglycans from commensal microorganisms and pathogens and coordinate signalling events that culminate in the induction of inflammation and anti-microbial responses. However, the signalling mechanisms involved in this process are not fully understood. Here, using genome-wide RNA interference, we identify candidate genes that modulate the NOD1 inflammatory response in intestinal epithelial cells. Our results reveal a significant crosstalk between innate immunity and apoptosis and identify BID, a BCL2 family protein, as a critical component of the inflammatory response. Colonocytes depleted of BID or macrophages from Bid(-/-) mice are markedly defective in cytokine production in response to NOD activation. Furthermore, Bid(-/-) mice are unresponsive to local or systemic exposure to NOD agonists or their protective effect in experimental colitis. Mechanistically, BID interacts with NOD1, NOD2 and the IκB kinase (IKK) complex, impacting NF-κB and extracellular signal-regulated kinase (ERK) signalling. Our results define a novel role of BID in inflammation and immunity independent of its apoptotic function, furthering the mounting evidence of evolutionary conservation between the mechanisms of apoptosis and immunity.     

Phagocytosis and clearance of apoptotic cells is mediated by MER

Apoptosis is fundamental to the development and maintenance of animal tissues and the immune system. Rapid clearance of apoptotic cells by macrophages is important to inhibit inflammation and autoimmune responses against intracellular antigens. Here we report a new function for Mer, a member of the Axl/Mer/Tyro3 receptor tyrosine kinase family. mer(kd) mice with a cytoplasmic truncation of Mer had macrophages deficient in the clearance of apoptotic thymocytes. This was corrected in chimaeric mice reconstituted with bone marrow from wild-type animals. Primary macrophages isolated from mer(kd) mice showed that the phagocytic deficiency was restricted to apoptotic cells and was independent of Fc receptor-mediated phagocytosis or ingestion of other particles. The inability to clear apoptotic cells adequately may be linked to an increased number of nuclear autoantibodies in mer(kd) mice. Thus, the Mer receptor tyrosine kinase seems to be critical for the engulfment and efficient clearance of apoptotic cells. This has implications for inflammation and autoimmune diseases such as systemic lupus erythematosus.     

Altered thymic T-cell selection due to a mutation of the ZAP-70 gene causes autoimmune arthritis in mice

Rheumatoid arthritis (RA), which afflicts about 1% of the world population, is a chronic systemic inflammatory disease of unknown aetiology that primarily affects the synovial membranes of multiple joints. Although CD4(+) T cells seem to be the prime mediators of RA, it remains unclear how arthritogenic CD4(+) T cells are generated and activated. Given that highly self-reactive T-cell clones are deleted during normal T-cell development in the thymus, abnormality in T-cell selection has been suspected as one cause of autoimmune disease. Here we show that a spontaneous point mutation of the gene encoding an SH2 domain of ZAP-70, a key signal transduction molecule in T cells, causes chronic autoimmune arthritis in mice that resembles human RA in many aspects. Altered signal transduction from T-cell antigen receptor through the aberrant ZAP-70 changes the thresholds of T cells to thymic selection, leading to the positive selection of otherwise negatively selected autoimmune T cells. Thymic production of arthritogenic T cells due to a genetically determined selection shift of the T-cell repertoire towards high self-reactivity might also be crucial to the development of disease in a subset of patients with RA.     

An explanation for the protective effect of the MHC class II I-E molecule in murine diabetes

Insulin-dependent diabetes mellitus is widely believed to be an autoimmune disease. Recent onset diabetics show destruction of insulin-secreting pancreatic beta-cells associated with a lymphocytic infiltrate (insulitis), with autoantibodies to beta-cells being found even before the onset of symptoms. Susceptibility to the disease is strongly influenced by major histocompatibility complex (MHC) class II polymorphism in both man and experimental animal models such as the non-obese diabetic (NOD) mouse. As MHC class II molecules are usually associated with dominant immune responsiveness, it was surprising that introduction of a transgenic class II molecule, I-E, protected NOD mice from insulitis and diabetes. This could be explained by a change either in the target tissue or in the T cells presumed to be involved in beta-cell destruction. Recently, several studies have shown that I-E molecules are associated with ontogenetic deletion of T cells bearing antigen/MHC receptors encoded in part by certain T-cell receptor V beta gene segments. To determine the mechanism of the protective effect of I-E, we have produced cloned CD4+ and CD8+ T-cell lines from islets of recently diabetic NOD mice. These cloned lines are islet-specific and pathogenic in both I-E- and I-E+ mice. Both CD4+ and CD8+ cloned T cells bear receptors encoded by a V beta 5 gene segment, known to be deleted during development in I-E expressing mice. Our data provide, therefore, an explanation for the puzzling effect of I-E on susceptibility to diabetes in NOD mice.     

Commensal microbiota and myelin autoantigen cooperate to trigger autoimmune demyelination

Active multiple sclerosis lesions show inflammatory changes suggestive of a combined attack by autoreactive T and B lymphocytes against brain white matter. These pathogenic immune cells derive from progenitors that are normal, innocuous components of the healthy immune repertoire but become autoaggressive upon pathological activation. The stimuli triggering this autoimmune conversion have been commonly attributed to environmental factors, in particular microbial infection. However, using the relapsing-remitting mouse model of spontaneously developing experimental autoimmune encephalomyelitis, here we show that the commensal gut flora-in the absence of pathogenic agents-is essential in triggering immune processes, leading to a relapsing-remitting autoimmune disease driven by myelin-specific CD4(+) T cells. We show further that recruitment and activation of autoantibody-producing B cells from the endogenous immune repertoire depends on availability of the target autoantigen, myelin oligodendrocyte glycoprotein (MOG), and commensal microbiota. Our observations identify a sequence of events triggering organ-specific autoimmune disease and these processes may offer novel therapeutic targets.     

Abnormal differentiation of thymocytes in mice treated with cyclosporin A

Cyclosporin A (CsA) acts as a powerful immunosuppressive agent, and also, when given in repeated doses, can cause T-cell-dependent graft-versus-host disease and organ-specific autoimmune disease in rodents. This suggests that CsA interferes with the processes governing self-tolerance, either by nullifying the activity of T suppressor cells or by preventing the deletion of autoreactive T cells during ontogeny in the thymus. We report here that irradiated mice given repeated injections of CsA show striking dysfunction of the thymus. There are two different effects, the first of which is that CsA seems to block the differentiation of immature CD4+CD8+ thymocytes into mature CD4+CD8- and CD4-CD8+ cells expressing a high density of T-cell receptors and CD3 molecules. Second, CsA-treated mice show incomplete deletion of T cells expressing T-cell receptor molecules reactive to self H-2 I-E molecules.     

Structural basis for co-stimulation by the human CTLA-4/B7-2 complex

Regulation of T-cell activity is dependent on antigen-independent co-stimulatory signals provided by the disulphide-linked homodimeric T-cell surface receptors, CD28 and CTLA-4 (ref. 1). Engagement of CD28 with B7-1 and B7-2 ligands on antigen-presenting cells (APCs) provides a stimulatory signal for T-cell activation, whereas subsequent engagement of CTLA-4 with these same ligands results in attenuation of the response. Given their central function in immune modulation, CTLA-4- and CD28-associated signalling pathways are primary therapeutic targets for preventing autoimmune disease, graft versus host disease, graft rejection and promoting tumour immunity. However, little is known about the cell-surface organization of these receptor/ligand complexes and the structural basis for signal transduction. Here we report the 3.2-A resolution structure of the complex between the disulphide-linked homodimer of human CTLA-4 and the receptor-binding domain of human B7-2. The unusual dimerization properties of both CTLA-4 and B7-2 place their respective ligand-binding sites distal to the dimer interface in each molecule and promote the formation of an alternating arrangement of bivalent CTLA-4 and B7-2 dimers that extends throughout the crystal. Direct observation of this CTLA-4/B7-2 network provides a model for the periodic organization of these molecules within the immunological synapse and suggests a distinct mechanism for signalling by dimeric cell-surface receptors.