Demethylation of TNFSF7 contributes to CD70 overexpression in CD4+ T cells from patients with systemic sclerosis

The pathogenesis of systemic sclerosis (SSc) is still unclear. CD70, a B cell costimulatory molecule that interacts with CD27 during B–T cell contact, is overexpressed due to demethylation of its promoter regulatory elements in CD4+ T cells from patients with the following autoimmune diseases, namely systemic lupus erythematosus (SLE), subacute cutaneous lupus erythematosus (SCLE) and primary Sjögren's syndrome (pSS). However, as an autoimmune disease, it is unknown whether aberrant expression and methylation of CD70 occur in SSc CD4+ T cells.     

Murine lupus in MRL/lpr mice lacking CD4 or CD8 T cells

MRL/lpr mice develop a systemic autoimmune disease similar to systemic lupus erythematosus in humans. The mice show progressive lymphadenopathy due to the accumulation of an unusual population of CD4^?8^?(DN) B220⁺ αβ⁺ T cells. We bred MRL/lpr mice with mice lacking CD4⁺ or CD8⁺ T cells by gene targeting via homologous recombination in embryonal stem cells to determine the roles of these cells in the autoimmune disease. No difference in survival or autoantibody levels was noted between CD8-/- lpr and littermate controls. Interestingly, these CD8-/- lpr mice have a reduced level of B220⁺ DN T cells despite the fact that the degree of lymphadenopathy was unaltered. CD4-/- lpr mice had a diminished autoimmune disease with a reduction in autoantibody production and skin vasculitits, and increased survival compared to littermate controls. However, CD4-/- lpr mice had an enhanced splenomegaly that developed massively by 16–20 weeks of age (5 to 8 greater than lpr control mice) due to the accumulation of DN B220⁺ T cells. In addition, there were no differences in peripheral lymph node enlargement, although the proportion of DN B220⁺ T cells was about twofold higher in the CD4-/- lpr mice. These cells were phenotypically identical to the DN population in control lpr mice, indicating that the accumulating DN T cells can be dissociated from the autoimmune disease in these mice. Collectively, our results reveal that the autoimmune disease is dependent on CD4⁺, but not CD8⁺ T cells, and that many of the B220⁺ DN T cells traverse a CD8 developmental pathway.     

DNA甲基化在急性冠脉综合征患者CD4+CD28-T细胞CD28表达缺失中的作用

目的 通过研究急性冠脉综合征(acute coronary syndrome,ACS)患者外周血CD4+T细胞CD28 mRNA水平和CD28基因启动子调节序列的甲基化状态,旨在探讨DNA甲基化在ACS患者CD4+CD28-T细胞CD28表达缺失中的作用.方法 免疫磁珠分离CD4+T细胞经逆转录后,实时定量PCR(real time-PCR)技术检测CD4+T细胞CD28mRNA的表达水平,亚硫酸氢钠测序检测CD28基因启动子调节序列的甲基化状态.结果 与正常对照组相比,ACS患者CD4+T细胞CD28mRNA表达水平显著减低,差异具有统计学意义[正常对照组比ACS组:(1.066±0.162)比(0.401±0.069),P<0.05].CD28基因启动子区域的甲基化水平显著增高,差异有统计学意义[正常对照组比ACS组:(24.47±3.17)%比(43.33±1.52)%,P<0.05].CD28基因启动子区域DNA甲基化水平与CD28mRNA表达水平呈显著负相关(P=0.01,r=-0.579).结论 ACS患者CD4+T细胞CD28基因启动子区域高甲基化调控了CD28基因转录抑制.DNA甲基化参与了CD4+CD28-T细胞的形成.     

Vaccination with autoreactive CD4Th1 clones in lupus-prone MRL/Mp-Fas mice

We studied the efficacy of T cell vaccination with CD4⁺αβTh1 clones in lupus-prone MRL/Mp-Fas^lpr/lpr (MRL/lpr) mice. CD4⁺αβ Th1 clones, dna51 (Vβ8.3) and rnp2 (Vβ14), which stimulated anti-dsDNA or U1 ribonucleoprotein (U1RNP) antibody (Ab) production respectively, were isolated from splenocytes of MRL/lpr mice. Antinuclear Ab kinetics, renal function, renal histology, survival rate, and lymphocyte subpopulations in the spleen were monitored after intravenous adoptive transfer of IL-2-stimulated (s-) or irradiated (i-) clones to 3 week-old female MRL/lpr mice. Anti-idiotypic humoral and T cell responses against the transferred autoreactive Th1 clones were determined in parallel. Compared with PBS-treated MRL/lpr mice, anti-dsDNA Ab titers, and the activity index for lupus nephritis were all decreased in MRL/lpr mice vaccinated with i-dna51 cells, whereas survival rate was not improved. The numbers of CD4⁺Vβ8.3 T cells in the spleen were also significantly decreased in these mice. Anti-idiotypic Abs recognizing a 12 amino acid sequence of clone dna51 T cell receptor Vβ8.3-complementarity-determining region (CDR) 3 were detected in the MRL/lpr mice that received i-dna51 or s-dna51 cells. These Abs suppressed dna51 cell proliferation, as well as cytotoxicity of CD8⁺T cells against dna51. The present study suggests that vaccination with CD4⁺αβTh1 clone, dna51, elicits anti-idiotypic T cell and humoral responses against dna51 in MRL/lpr mice, although the immunoregulatory effects on lupus may be limited.     

CD4+CD28-T细胞DNA甲基化异常与免疫系统疾病的关系

在急性冠脉综合征(ACS)和一些自身免疫性疾病中发现CD4+ CD28-T细胞,该细胞具有细胞毒性,抵抗细胞凋亡和浸润组织能力.CD4+ CD28-T细胞内的DNA甲基化异常可导致一些基因的过度表达,与疾病的发生发展密切相关.深入研究CD4+ CD28-T细胞功能特性及CD4+CD28-T细胞内DNA甲基化在疾病中的作用,有利于阐明疾病的发病机制,为治疗疾病提供新的线索.     

Interferon regulatory factor-1 gene deletion decreases glomerulonephritis in MRL/lpr mice

To investigate the role of interferon regulatory factor-1 (IRF-1) in the development of lupus nephritis, IRF-1(-/-) genotype mice were bred onto the MRL/lpJfas(lpr) (MRL/lpr) background. We examined kidney mesangial cell function and disease progression. Endpoints evaluated included inflammatory mediators, autoantibody production, immune complex deposition, renal pathology, T cell subset analysis, and duration of survival. Mesangial cells cultured from IRF-1(-/-) mice produced significantly lower levels of nitric oxide and IL-12 but not TNF-alpha when stimulated with LPS + IFN-gamma. IRF-1(-/-) mice showed less aggravated dermatitis compared to the wild-type mice. Anti-double-stranded DNA production and proteinuria were significantly decreased in IRF-1(-/-) mice compared to IRF-1(+/+) mice. IgG and C3 deposition as well as glomerulonephritis were decreased in IRF-1(-/-) mice at 26 wk of age compared to the IRF-1(+/+) mice. Splenic CD4- CD8- CD44+ T cells were decreased while CD4+ CD25+ T cells were increased in the IRF-1(-/-) mice when compared to IRF-1(+/+) mice. Survival rates (ED50) were 22 wk for IRF-1(+/+) mice and 45 wk for IRF-1(-/-) mice. These findings suggest an important role of IRF-1 in mediating renal disease in MRL/lpr mice.     

Subpopulations of CD4+ cells in lpr/lpr mice: differences in expression of T cell receptor/CD3 complex and proliferative responses.

CD4+ cells from autoimmune-prone C57BL/6 lpr/lpr mice contain two subpopulations, B220-CD4+ and B220+CD4+ cells. Highly purified B220-CD4+ cells from C57BL/6 +/+ and lpr/lpr mice were examined by comparing functional characteristics and expression of cell surface antigens and T cell receptor (TcR)/CD3 complex. Both lpr B220+CD4+ and B220+CD4-CD8- cells, most of which were PgP-1 positive, expressed TcR/CD3 complex on the cell surface at lower level as compared with B220-CD4+ cells of age-matched normal mice. In addition, the B2200-CD4+ cells were heterogeneous on the basis of surface expression of PgP-1 and CD3 antigens. Normal levels of TcR C alpha-, C beta- and V beta 8-specific mRNA were found in the B220-CD4+ cells and B220+CD4+ cells as compared with normal B220-CD4+ cells, while V beta 8-specific mRNA was preferentially expressed only by B220+CD4-CD8- cells. Either B220+CD4+ cells and B220+CD4-CD8- cells failed to respond to anti-CD3 monoclonal antibody (MoAb) as assessed by proliferative responses and production of interleukin-2 (IL-2). However, appreciable levels of reactivity to anti-CD3 MoAb were detected in the B220-CD4+ cells, although the responsiveness of this subset to such stimuli were reduced, compared with those of normal control. These results indicate that the B220-CD4+ cells in lpr mice are phenotypically and functionally distinct from normal B220-CD4+ cells.     

三氧化二砷对MRL/lpr狼疮鼠抗ds-DNA抗体和淋巴细胞亚群的影响

目的研究三氧化二砷(ATO)对MRL/lpr狼疮鼠抗ds-DNA抗体和淋巴细胞亚群的影响。方法将MRL/lpr狼疮鼠随机分为:ATO组、生理盐水(NS)组和环磷酰胺(CTX)组。另设正常C57/BL小鼠,随机分为ATO治疗组(0.4 mg/kg.d)和对照组(0.25 mL)。以上每组各6只,隔日腹腔注射,给药2个月后处死,称体重和脾脏重量算出脾脏指数;ELISA法测各组小鼠血清抗ds-DNA抗体水平;流式细胞术测脾脏细胞亚群百分比。结果(1)MRL/lpr小鼠ATO治疗组脾脏指数、血清抗ds-DNA抗体水平和CD19 、CD3 、CD3 CD4 细胞百分比均低于NS对照组(P<0.01或P<0.05),NK细胞百分比明显高于NS对照组(P<0.05);(2)ATO治疗组小鼠的脾脏指数和CD3CD4双阳性细胞百分比显著低于CTX组(P<0.01),CTX治疗组小鼠血清抗ds-DNA抗体水平均较对照组明显降低(P<0.01),但ATO治疗组的抗体水平较CTX治疗组高(P<0.05);(3)在C57/BL小鼠中,ATO治疗组和NS治疗组之间以上指标均无差异。结论ATO抑制MRL/lpr狼疮鼠T、B淋巴细胞活化同时上调NK细胞功能,减少体内自身抗体产生;但是对正常小鼠的抗体水平和细胞亚群并无明显影响。     

Correlation between miR-126 expression and DNA hypomethylation of CD4+ T cells in rheumatoid arthritis patients

It has been known that the occurrence of rheumatoid arthritis (RA) was closely correlated with DNA hypomethylation in CD4+ T cells, in which DNA methyltransferase plays a certain role. This study therefore investigated the effect of miR-126 on CD4+ T cell subgroup in RA patients and the alternation of DNA hypomethylation, in an attempt to provide new sights into the pathogenesis and treatment of RA. CD4+ T cells separated from RA patients were transfected with miRNA (miR)-126 expression vector or miR-126 inhibitor expression vector. The expression levels of CD11a, CD70 and DNMT1 mRNA were examined by real-time PCR. Protein levels of CD11a and CD70 were tested by flow cytometry while DNMT1 protein level was quantified by Western blotting. DNA was modified by sodium bisulfite and was sequenced for the methylation status of promoters of CD11a and CD70 genes. Both mRNA and protein expressions of CD11a and CD70 genes in CD4+ T cells were elevated by miR-126 transfection, along with decreased DNMT1 protein level but not mRNA level. The methylation degree of promoters of both CD11a and CD70 genes were significantly depressed after miR-126 transfection. The transfection by miR-126 inhibitor effectively reversed such effects. In RA patients, elevated miR-126 may promote the expression of CD11a and CD70 via the induction of hypomethylation of gene promoters by depressing DNMTI1 protein levels.     

Increased expression of CD80, CD86 and CD70 on T cells from HIV-infected individuals upon activation in vitro: regulation by CD4+ T cells

T cells express CD28 and CD27 which transduce co-stimulatory signals after interaction with their ligands on antigen-presenting cells (APC). These ligands, CD80, CD86 and CD70, are also expressed to some extent on activated T cells. Here, we show that in human immunodeficiency virus (HIV)-infected individuals, CD28 and CD27 expression is decreased on CD8⁺ T cells. On the other hand, T cell stimulation in vitro induced high CD80, CD86 and CD70 expression on T cells from HIV-infected individuals. It appeared that an inverted CD4:CD8 T cell ratio could explain this enhanced expression of co-stimulatory ligands. Indeed, high expression levels of CD80, CD86 and CD70 were found on activated CD8⁺ T cells from HIV⁻ individuals cultured in the absence of CD4⁺ T cells. Addition of CD4⁺ T cells prevented this up-regulation. However, in HIV-infected individuals, addition of excess autologous or healthy control CD4⁺ T cells did not completely counteract up-regulation of co-stimulatory ligand expression on CD8⁺ T cells. Thus, to some extent, CD8⁺ T cells in HIV-infected individuals appeared to be refractory to CD4⁺ T cell-mediated regulation of ligand expression in vitro. Activated T cells from HIV-infected individuals and activated CD8⁺ T cells from healthy controls were able to act as accessory cells in CD3-induced T cell proliferation, which was dependent on cell-cell contact. Thus, we showed that T cells from HIV-infected individuals express enhanced levels of co-stimulatory ligands upon activation, which provides them with accessory cell properties. Enhanced stimulatory potential of these nonprofessional APC may contribute to persistently high levels of immune activation in HIV infection related to disease progression.     

lpr T cells vaccinate against lupus in MRL/lpr mice.

MRL/MP-lpr/lpr mice are homozygous for the lpr mutation that results in the accumulation of phenotypically abnormal cells (CD3+CD4+CD8-) in all lymphoid issues. Although no major abnormalities in the T cell receptor repertoire expressed by such lpr cells have been reported, the lpr mutation is a major disease-accelerating factor. Finally, intravenous administration of irradiated lpr cells recovered from the hyperplastic lymph nodes of adult diseased animals to young MRL/Mp-lpr/lpr mice resulted in a highly significant amelioration of disease parameters. This "T cell vaccination" approach resulted in a selective depletion of cells expressing products of the V beta 8.2 subfamily among lymph node T cells, in addition to eliciting a surge in peripheral T cells capable of conferring disease protection in adoptive transfer experiments. Thus, a strategy aimed at specifically reducing the frequency of lpr cells proved successful in mitigating the autoimmune process. These findings add to the involvement of lpr cells in the autoimmune process and constitute the first report that T cell vaccination may be beneficial to a spontaneously occurring autoimmune disease.     

CD4+ T cells epigenetically modified by oxidative stress cause lupus-like autoimmunity in mice

Lupus develops when genetically predisposed people encounter environmental agents such as UV light, silica, infections and cigarette smoke that cause oxidative stress, but how oxidative damage modifies the immune system to cause lupus flares is unknown. We previously showed that oxidizing agents decreased ERK pathway signaling in human T cells, decreased DNA methyltransferase 1 and caused demethylation and overexpression of genes similar to those from patients with active lupus. The current study tested whether oxidant-treated T cells can induce lupus in mice. We adoptively transferred CD4⁺ T cells treated in vitro with oxidants hydrogen peroxide or nitric oxide or the demethylating agent 5-azacytidine into syngeneic mice and studied the development and severity of lupus in the recipients. Disease severity was assessed by measuring anti-dsDNA antibodies, proteinuria, hematuria and by histopathology of kidney tissues. The effect of the oxidants on expression of CD40L, CD70, KirL1 and DNMT1 genes and CD40L protein in the treated CD4⁺ T cells was assessed by Q-RT-PCR and flow cytometry. H₂O₂ and ONOO⁻ decreased Dnmt1 expression in CD4⁺ T cells and caused the upregulation of genes known to be suppressed by DNA methylation in patients with lupus and animal models of SLE. Adoptive transfer of oxidant-treated CD4⁺ T cells into syngeneic recipients resulted in the induction of anti-dsDNA antibody and glomerulonephritis. The results show that oxidative stress may contribute to lupus disease by inhibiting ERK pathway signaling in T cells leading to DNA demethylation, upregulation of immune genes and autoreactivity.     

Methyl- rich diet ameliorates lupus-like disease in MRL/lpr mice

Genetic susceptibility is necessary but not sufficient for systemic lupus erythematosus (SLE) to appear indicating that environmental factors are also key components in the disease onset. Aberrant DNA methylation profile positively correlates with the development of lupus-like disease in MRL/lpr mice. In the present study, we evaluate the effect of long term administration of methyl-rich diet in MRL mice. The results showed that supplemented diet decreased the levels of proteinuria and of anti-dsDNA antibodies and modulated cytokine profiles. Limited kidney failure and prevented development of skin lesions in MRL/lpr mice were another positive effects of the high-dose methyl diet. These data suggest that it is possible to modulate the disease course by altering the amount of particular dietary micronutrients and that nutrition-mediated changes in DNA methylation may have potential clinical relevance.     

Alteration of DNA methylation levels in MRL lupus mice

Recent reports suggest that DNA methylation is involved in the cause of autoimmune disease. We investigated the alteration of DNA methylation levels in lupus strains of mice, MRL/lpr as a model, which develop an age-dependent lymphadenopathy and autoimmune disease. DNA methylation levels of thymus and axillary lymph nodes in 20-week-old MRL/lpr mice, which are in an autoimmune disease state, were lower than those of 4-week-old MRL/lpr mice with no symptoms as yet. No significant changes were observed in MRL/4- strain mice, which seemed normal at least 20 weeks, while DNA methylation levels in the spleen of both strains of mice increased significantly from the age of 4 to 20 weeks. However, no significant changes of DNA methylation levels in peripheral blood were observed with ageing in MRL strains. Moreover, we clarified that administration of 5-azacytidine had a strong effect on longer survival of MRL/lpr mice and reduced DNA methylation levels in the axillary lymph nodes and spleen. The possible relevance of DNA methylation levels to the progression of autoimmune disease is discussed.     

Differences between CD8+ T cells in lupus-prone (NZB x NZW) F1 mice and healthy (BALB/c x NZW) F1 mice may influence autoimmunity in the lupus model

Immunization with portions of a murine antibody to DNA induced Ig peptide-reactive peripheral CD8+ inhibitory T (Ti) cells in non-autoimmune (BALB/c x NZW) F1 (CWF1) mice. Those Ti suppressed in vitro production of IgG anti-DNA by lymphocytes from MHC-matched, lupus-prone (NZB x NZW) F1 (BWF1) mice, primarily via secretion of transforming growth factor-beta (TGF-beta). However, splenic CD8+ cells from immunized BWF1 mice failed to suppress anti-DNA. Therefore, BWF1 mice were studied for defects in peripheral CD8+ T cells. The potential to suppress autoimmunity mediated by activated CD4+ helper T and B cells in BWF1 mice was assessed. As BWF1 mice aged, peripheral CD8+ T cells expanded little; fewer than 10% displayed surface markers of activation and memory. In contrast, quantities of splenic CD4+ T and B cells increased; high proportions displayed activation/memory markers. In old compared to young BWF1 mice, splenic cell secretion of two cytokines required for generation of CD8+ T effectors, IL-2 and TGF-beta, was decreased. Immunizing BWF1 mice activated peptide-reactive CD8+ T cells, but their number was decreased compared to young BWF1 or old normal mice. While peptide-reactive splenic CD8+ T cells from immunized BWF1 mice did not survive in short-term cultures, similar CD8+ T cell lines from immunized CWF1 mice expanded and on transfer into BWF1 mice delayed autoimmunity and prolonged survival. Therefore, CD8+ T cells in old BWF1 mice are impaired in expansion, acquisition of memory, secretion of cytokine, and suppression of autoimmunity. Understanding these defects might identify targets for therapy in systemic lupus erythematosus.     

CD1d deficiency exacerbates inflammatory dermatitis in MRL-lpr/lpr mice

Mechanisms responsible for the development of autoimmune skin disease in humans and animal models with lupus remain poorly understood. In this study, we have investigated the role of CD1d, an antigen-presenting molecule known to activate natural killer T cells, in the development of inflammatory dermatitis in lupus-susceptible MRL-lpr/lpr mice. In particular, we have established MRL-lpr/lpr mice carrying a germ-line deletion of the CD1d genes. We demonstrate that CD1d-deficient MRL-lpr/lpr mice, as compared with wild-type littermates, have more frequent and more severe skin disease, with increased local infiltration with mast cells, lymphocytes and dendritic cells, including Langerhans cells. CD1d-deficient MRL-lpr/lpr mice had increased prevalence of CD4(+) T cells in the spleen and liver and of TCR alpha beta (+)B220(+) cells in lymph nodes. Furthermore, CD1d deficiency was associated with decreased T cell production of type 2 cytokines and increased or unchanged type 1 cytokines. These findings indicate a regulatory role of CD1d in inflammatory dermatitis. Understanding the mechanisms by which CD1d deficiency results in splenic T cell expansion and cytokine alterations, with increased dermal infiltration of dendritic cells and lymphocytes in MRL-lpr/lpr mice, will have implications for the pathogenesis of inflammatory skin diseases.     

Glomerular overexpression and increased tyrosine phosphorylation of focal adhesion kinase p125FAK in lupus-prone MRL/MP-lpr/lpr mice

Much progress has been made in understanding how mammalian cells receive a diverse array of external stimuli and convert them into intracellular biochemical signals. Such efforts have identified a large number of signalling molecules. However, our knowledge is limited as to their pathophysiological role in particular diseases. We demonstrate herein that an integrin-linked signalling molecule, focal adhesion kinase p125FAK (FAK), is overexpressed in glomeruli of lupus-prone MRL/MP-lpr/lpr (MRL-lpr) mouse as compared to its congeneic MRL-+/+ strain. Increased expression was specifically demonstrated in glomeruli but not in other tissues examined. The overexpression was observed in 16-week-old MRL-lpr mice with active nephritis, as well as in younger animals at 4 weeks of age. Thus, the upregulation of FAK clearly preceded the clinical onset of nephritis. FAK in MRL-lpr glomeruli is highly tyrosine phosphorylated and is associated with adapter protein Grb2. Previous in vitro studies have shown that the association of FAK/Grb2 links cell adhesion to the Ras pathway, which ultimately stimulates mitogen-activated protein (MAP) kinase, an important regulator of cell proliferation. In accordance, we observed constitutive MAP kinase activation in MRL-lpr glomeruli. Our findings suggest that signalling pathways involving FAK are activated in MRL-lpr glomeruli, and are likely to play a role in the development and progression of autoimmune-mediated murine nephritis.     

HSP70/CD80嵌合DNA疫苗对哮喘小鼠气道炎症和气道高反应性的作用

目的 研究HSP70/CD80嵌合DNA质粒对哮喘小鼠气道炎症和气道高反应性的作用,为安全可靠的新型免疫调节性疫苗奠定基础.方法 将40只雌性健康BALB/c小鼠随机分为4组:对照组、哮喘组、pcDNA3.1载体组、HSP70/CD80嵌合DNA疫苗组,每组10只.用HSP70/CD80嵌合疫苗免疫小鼠后,建立鸡卵清蛋白致敏的小鼠哮喘模型,观察其气道阻力变化,支气管肺泡灌洗液中IL-13、IFN-γ含量的变化.取肺组织进行病理组织学分析,观察肺内炎症情况.结果 HSP70/CD80嵌合DNA疫苗免疫小鼠后,能有效减轻气道炎症(P＜0.05),降低气道阻力(P＜0.05),肺泡灌洗液中IFNl的分泌增加(P＜0.05),IL-13降低.结论 HSP70/CD80嵌合DNA疫苗可促进免疫反应向Th1偏移并增加IFN-γ的生成,减轻气道炎症,降低气道阻力,这为过敏性哮喘新型免疫调节性疫苗的机制及应用研究提供了实验资料.     

An increased frequency of autoantibody-inducing CD4+ T cells in pre-diseased lupus-prone mice

Pathogenic autoantibody production in murine models of lupus is dependent on autoreactive CD4+ helper T cells. However, the mechanisms which permit the selection and maintenance of this autoantibody-inducing CD4+ T-cell repertoire are currently unknown. We hypothesized that the peripheral CD4+ T-cell repertoire of lupus-prone mice was enriched with autoantibody-inducing specificities. To test this, we utilized the splenic focus assay to determine if pre-diseased lupus-prone (NZB x NZW)F(1) mice have an elevated frequency of autoreactive CD4+ T lymphocytes capable of supporting autoantibody production. The splenic focus limiting dilution assay permits anti-nuclear antibodies to be generated from contact-dependent T-B interactions in vitro. We show that young, pre-diseased lupus-prone mice have an elevated frequency of autoantibody-inducing CD4+ T cells. Interestingly, these autoantibody-inducing CD4+ T-cell responses are also present in the thymus. Therefore, an elevated frequency of autoantibody-inducing CD4+ T cells predisposes lupus-prone mice to the development of autoantibodies.