Defective DNA methylation and CD70 overexpression in CD4+ T cells in MRL/lpr lupus-prone mice

We have determined that abnormal DNA methylation in T cells coincides with the development of autoimmunity, using a mouse model that exhibits an age-dependent lupus-like disease (MRL/lpr mice). Splenic CD4(+) T cells were isolated from these mice at 5 and 16 wk of age (before and after autoimmunity is established) and the expression of DNA methyltransferase 1 (Dnmt1) and the methylation-sensitive gene Tnfsf7 (CD70) was measured. Bisulfite DNA sequencing was used to monitor the methylation status of the Tnfsf7 gene. We found that Dnmt1 steady-state mRNA levels were significantly lower in 16-wk-old MRL/lpr mice, which had established autoimmunity, compared to the 5-wk-old MRL/lpr mice. Furthermore, the expression of CD70 was higher in MRL/lpr mice at 16 wk. CD70 was overexpressed in MRL/lpr mice compared to age- and sex-matched MRL(+/+) controls. Bisulfite DNA sequencing of the Tnfsf7 gene in MRL/lpr mice revealed that at 16 wk, CG pairs were hypomethylated compared to 5-wk-old mice, and that Tnfsf7 from MRL/lpr mice was hypomethylated at 16 wk relative to age-matched MRL(+/+) controls. Our data indicate that decreased expression of Dnmt1 and the corresponding T cell DNA hypomethylation correlate with the development of age-dependent autoimmunity in MRL/lpr mice.     

MRL/lpr狼疮小鼠肾脏明胶酶表达随增龄变化及意义

目的 观察不同周龄MBL/lpr狼疮小鼠肾脏明胶酶的表达及其随增龄而发生的活性变化及意义。方法 取8、16与24周龄RMRL/lpr狼疮小鼠的肾组织进行常规病理检测。利用含有放射自显影的成像乳胶对冷冻肾组织切片进行原位明胶酶活性的检测;利用免疫组织化学检测肾脏明胶酶A与明胶酶B的酶B的蛋白表达变化,十二氨基磺酸钠-聚丙烯酰胺凝胶电泳（SDS-PACE）明胶酶谱法检测肾脏明胶酶A、B的活性变化。结果 8周龄狼疮小鼠肾组织吵仅在血管处检测到明胶酶的活性;16与24周龄狼疮小鼠肾小球内明胶酶的净活性明显增加。在肾小球以及肾小管间质上也可检测到明胶酶的活性,乙二胺四乙酸（EDTA）能够抑制肾脏明胶酶的活性,免疫组织化学与SDS-PAGE明胶酶谱法结果显示其肾组织中明胶酶A与明胶酶B的蛋白质表达及活性均明显增加。结论 明胶酶A、B在自发性狼疮小鼠肾炎中的表达及活化随增龄均明显增加,活化态的明胶酶可能在狼疮性肾炎细胞外基质重塑中发挥重要的作用。     

Altered Th1/Th2 commitment in human CD4+ T cells with ageing

The human immune system undergoes continuous remodelling with the advancement of age. Since age-associated functional alterations in the immune system could be caused by a possible change in helper T cell regulation in elderly subjects, we comparatively studied the function of CD4+ T cells in peripheral blood obtained from both young and old healthy volunteers. Upon cell activation by phorbol myristate acetate and ionomycin, the proportion of CD4+ T cells containing interferon-gamma (IFN-gamma) was found to be greater in the old subjects. Utilizing a co-culture system, which activated CD4+ T cells via the TCR/CD3 complex and CD28, we found that CD4+ T cells from the old subjects secreted more IFN-gamma and IL-2, but less IL-4, than those from the young subjects. Upon cell activation by co-culture, CD4+ T cells from the old subjects expressed more CD26, CD40L, and LFA-1, but less CD30, than those from the young. These results together suggest that the microenvironment in which CD4+ T cells develop in older people may cause production of more cells committed to Th1 than that in younger subjects.     

T cell receptor specificities of Toxoplasma gondii-reactive mouse CD4+ T lymphocytes and Th1 clones

The Toxoplasma gondii-directed CD4⁺ T cell response in chronically infected mice was studied with respect to both T cell receptor diversity and antigen specificities. T cell receptor chains Vβ4, 6, 8, 10, and 14 were predominantly found on toxoplasma-reactive CD4⁺ splenocytes. This repertoire was also detected among T. gondii-specific CD4⁺ T cell clones. Analysis of clonotypic cytokine profiles revealed typical Th1 clones secreting interleukin-2, interferon-γ and tumour necrosis factor activity and Th2 clones producing interleukin-4 and interleukin-10. Five distinct toxoplasma antigens (p26, p40, p55, p58 and p60) were detected in electrophoretically separated toxoplasma lysate by five individual Th1 clones. Parallel testing of CD4⁺ T lymphocytes from infected mice confirmed that these specificities constitute the peak immunogenic fractions of toxoplasma lysate. The expression patterns of two clonotypic, T cell-stimulatory parasite antigens were studied in detail. While p55 was expressed by mouse-virulent and avirulent T. gondii isolates and in both the tachyzoite and bradyzoite stages, p58 was detected only in virulent strains from intraspecies subgroup I. Thus, we describe the heterogeneity of toxoplasmic immunodominant T cell antigens including a 58-kDa group I-restricted molecule which may provide a marker for virulent isolates. Received: 3 February 1997     

白细胞介素17 在狼疮性肾炎小鼠中的表达及抗白细胞介素17抗体的干预作用

 目的:探讨白细胞介素17（IL-17）在狼疮性肾炎(LN）小鼠中的表达及抗IL-17抗体的干预作用。方法:11周龄的雌性MRL/lpr小鼠36只随机分为实验组和干预组,另有同龄雌性昆明小鼠18只为对照组。干预组每只小鼠腹腔注射抗小鼠IL-17多克隆抗体20 μg,每2周1次,至实验观察点结束。各组分别于第1次给药后的24 h、14 d及28 d处死6只小鼠。光镜下观察肾脏病理情况,ELISA法检测小鼠血清IL-17的含量,免疫组化法检测肾组织IL-17的表达水平。结果:MRL/lpr小鼠肾小球系膜细胞及基质弥漫增生,肾小管上皮细胞颗粒及空泡变性,灶状萎缩,肾间质淋巴及单核细胞浸润伴纤维化;而干预组肾脏病理改变较实验组为轻。MRL/lpr小鼠的血清IL-17含量在实验组各时点均显著高于对照组（P<0.05）,而在干预组各时点均显著低于实验组（P<0.05）。IL-17在实验组小鼠肾小管上皮细胞中的表达明显增强,在各时点均显著高于对照组（P<0.05）;在干预组,IL-17在各时点的表达均显著低于实验组（P<0.05）。结论:IL-17在MRL/lpr小鼠血清与肾组织中的表达显著增加,而抗IL-17抗体可通过抑制IL-17的表达而抑制LN的炎症免疫反应,减轻肾脏病理损害。     

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。     

CD4+CD25highFoxp3+ Treg deficiency in a Brazilian patient with Gaucher disease and lupus nephritis

Gaucher Disease (GD) is a rare autosomal recessive disorder caused by the deficient activity of beta-glucocerebrosidase. GD is one of the lysosomal storage diseases with the most remarkable alterations in the immune system, and that may manifest clinically as autoimmune disorders and malignancy. We reported the immunological evaluation of a patient with GD and lupus nephritis. Decreased absolute values of T, and NK, and an inversion of CD4⁺/CD8⁺ ratio, low levels of IgM and normal B cells were found when compared to reference values in a Brazilian population. Absence ofCD4⁺CD25^highFoxp3⁺ Treg and high levels of total NKT, iNKT cells and CD8⁺ iNKT subsets were also observed when compared to the healthy control and GD patient without lupus nephritis. Treg subset and CD8⁺ iNKT abnormalities might be involved in severe lupus nephritis in a GD patient. We conclude by emphasizing the importance of the immunological evaluation on early diagnosis of autoimmunity contributing to reduce mortality and morbidity of these patients.     

靶向骨桥蛋白的小干扰RNA对MRL/Lpr小鼠狼疮肾炎的治疗作用

目的观察骨桥蛋白(OPN)的小干扰RNA(si RNA)对SLE动物模型MRL/Lpr小鼠24 h尿蛋白、脾组织中Treg和Th17细胞的表达、肾脏的病理改变的影响,探讨OPN si RNA对狼疮肾炎的治疗作用。方法 25只MRL/Lpr小鼠随机分为对照组、空载体组、OPN-si RNA1组、OPN-si RNA2组及OPN-si RNA3组,每组5只,RT-PCR法检测小鼠肾脏组织中OPN m RNA的表达水平;免疫组化法检测小鼠肾脏组织中OPN蛋白的表达水平;考马斯亮蓝染色法检测24 h尿蛋白含量;ELISA法检测小鼠血清中抗ds DNA抗体水平;流式细胞术检测小鼠脾组织中Treg细胞和Th17细胞的表达水平;病理切片苏木精-伊红(HE)染色法观察5组小鼠肾脏的病理变化。结果 OPN si RNA表达载体可以在MRL/Lpr小鼠的肾脏中表达;注射后6周OPN-si RNA1组、OPN-si RNA2组和OPN-si RNA3组中MRL/Lpr小鼠肾脏组织中OPN m RNA和蛋白的表达水平明显低于对照组和空载体组,差异有统计学意义(P<0.05);MRL/Lpr小鼠的24 h尿蛋白含量和抗ds DNA抗体在治疗前5组没有差异,OPN-si RNA作用后2周和4周小鼠24 h尿蛋白含量和抗ds DNA抗体水平下降,随着OPN-si RNA作用时间的延长小鼠24 h尿蛋白含量和抗ds DNA抗体水平逐渐下降,注射后6周MRL/Lpr小鼠的24 h尿蛋白含量和抗ds DNA抗体开始升高,但仍低于对照组和空载体组,差异有统计学意义(P<0.05);OPN-si RNA作用后MRL/Lpr小鼠脾组织中Th17细胞占CD4+T细胞的百分比明显下降,而Treg细胞占CD4+T细胞的百分比上升,与对照组和空载体组比较差异有统计学意义(P<0.05);OPN-si RNA作用后肾小球减小、肾小球的浸润的炎性细胞减少,与对照组和空载体组比较差异有统计学意义(P<0.05)。结论 MRL/Lpr小鼠注射OPN si RNA载体后,OPN m RNA和蛋白的表达水平下降,24 h尿蛋白含量和抗ds DNA抗体水平下降,脾组织中Th17细胞的百分比下降,Treg细胞的百分比上升,肾脏中炎性细胞的浸润减少,说明OPN si RNA可调节狼疮小鼠Th17/Treg细胞的平衡并对狼疮肾炎有一定的治疗作用。     

G1 arrest and high expression of cyclin kinase and apoptosis inhibitors in accumulated activated/memory phenotype CD4+ cells of older lupus mice

A general characteristic of lupus-prone mice (and humans) is the expedited accumulation of large numbers of presumably self-reactive activated/memory phenotype T cells. The mechanism by which these cells escape apoptosis has not been defined. We used activated/memory phenotype CD4⁺ cells from male BXSB mice with early-life severe lupus-like disease to investigate cell cycle status and apoptosis susceptibility, and to determine the role of corresponding genes in survival of these cells. In vitro acridine orange staining indicated that most of the rapidly accumulating memory phenotype CD4⁺ T cells of 4-month-old male BXSB mice are G1 arrested. Long-term bromodeoxyuridine in vivo labeling also showed that with advanced age, there was a shift of the CD4⁺ CD44^hi male cells from predominantly cycling to predominantly noncycling. Moreover, the CD4⁺ CD44^hi cells of older males were refractory to anti-CD3-induced proliferation and apoptosis. Using a multiprobe RNase protection assay encompassing riboprobe panels for cell cycle and apoptosis-related genes, we found that these cells exhibited high expression of certain members of the Ink4 (p18^Ink4C) and Cip/Kip (p21^Cip1) families of cyclin kinase inhibitors as well as of the apoptosis-inhibiting Bcl-x_L gene. Western blot analysis confirmed increased levels of Bcl-x_L and p21^Cip1, and also identified increases in another cyclin kinase inhibitor, p27^Kip1. We propose that in autoimmunity, self-reactive CD4⁺ cells are subjected to successive rounds of activation/division that eventually lead to a build-up in cyclin-dependent kinase inhibitors. Once high levels of such inhibitors are reached, they cause refractoriness to further activation, impaired cell cycle entry and resistance to apoptosis, a situation akin to replicative senescence.     

卵清白蛋白特异性T细胞免疫诱导BALB/c小鼠的调节性免疫应答

目的：研究T细胞免疫后正常小鼠的调节性免疫应答，方法：应用体外扩增的卵清白蛋白（OVA）特异的T细胞克隆免疫BALB／c小鼠，3H－TdR掺入法分析细胞增殖，3H－TdR标记靶细胞检测杀伤T细胞的杀伤效应，间接免疫荧光法分析血清中抗T细胞抗体水平。结果：T细胞免疫后能诱导BALB/c小鼠产生调节性T细胞的增殖反应，对靶细胞的杀伤效应以及针对于活化的T细胞的体液免疫应答，并进一步降低机体对OVA抗原的应答，结论：T细胞免疫能诱导正常机体的调节性免疫应答。     

Accelerated expression of anti-Sm and Y2 idiotype differ in dependence on T cell subsets in MRL/+ mice.

We investigated the role of MRl T cells in the induction of anti-Sm antibodies and Y2 idiotype. Four injections of Sm antigen in Freund's complete adjuvant were required to induce peak amounts of specific anti-Sm antibody in young BALB/c and MRL/+ mice. The Y2 idiotype was expressed in MRL/+ mice but not in BALB/c mice. Expression of both anti-Sm, predominantly IgG2a heavy chain, and Y2 idiotype was augmented in MRL/+ mice after two injections of Sm if, prior to immunization, mice received splenic T cells from naive MRL/lpr or immunized, but not naive MRL/+ mice. These results suggest that the lpr gene contributes to the ability of autoimmune T cells to augment the anti-Sm antibody response. Treatment of primed MRL/+ donor T cells with anti-CD4, but not anti-CD8, antibodies and complement removed the ability to augment anti-Sm antibody production. In contrast, augmentation of Y2 idiotype production was abrogated by pretreatment of donor T cells with either anti-CD4 or anti-CD8. These results suggest that, while MRL/+ CD4+ T cells play an important role in anti-Sm antibody production, additional interaction between CD4+ and CD8+ T cells augments Y2 expression.     

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.     

Analysis of clones derived from human CD7+CD4-CD8-CD3- thymocytes.

The differentiation of human thymocyte precursors was studied by analysis of clonal progeny of CD4-CD8-CD3- (triple negative or TN) thymocytes. Using a culture system of phytohemagglutinin, IL-2, and irradiated allogeneic lymphoid feeder cells, we found that 48% of clones (104 total) derived from TN thymocyte suspensions were TCR gamma delta cells, 12% of clones were TCR alpha beta cells, and 34% were CD16+CD3- cells. Importantly, 6% of clones were novel subsets of CD4+CD8-CD3- or CD4-CD8+CD3- thymocytes. The majority of TCR alpha beta, TCR gamma delta, and CD16+CD3- clones expressed low levels of CD4. Molecular analysis of freshly isolated TN- thymocytes prior to in vitro culture demonstrated that up to 40% of cells had TCR gamma, delta, and beta gene rearrangements, but were negative in indirect immunofluorescence assays for cytoplasmic TCR delta and beta. These data provide evidence at the clonal level for the presence of precursors of the TCR alpha beta and TCR gamma delta lineages in the human TN thymocyte pool. Moreover, a substantial proportion of freshly isolated human TN thymocytes had already undergone TCR gene rearrangement prior to in vitro culture. Whether these precursors of the TCR alpha beta and TCR gamma delta lineages mature from cells already containing TCR gene rearrangements into sTCR+ cells or differentiate in vitro from cells with TCR genes in germline configuration remains to be determined. Nonetheless, these data demonstrate that the predominant clone types that grow out of human TN thymocytes in vitro are TCR gamma delta and NK cells.     

Pathogenesis of autoimmunity in αβ T cell-deficient lupus-prone mice

Murine lupus in MRL mice has been strongly attributed to αβ T cell-dependent mechanisms. Non-αβ T cell-dependent mechanisms, such as γδ T cells, have been shown to drive antibody and autoantibody production, but they have not been considered capable of inducing end-organ disease. Here, we have expanded upon the findings of such previous work by examining the mechanism and extent of end-organ disease attainable via γδ T cells and/or non-αβ T cell-dependent mechanisms, assessing two prototypical lupus lesions, renal and skin disease, in TCR α?/? MRL mice that possessed either functional or defective Fas antigen (Fas + or lpr). Observed to 1 year of age, TCR α?/? MRL mice developed disease characterized by increased mortality, overt renal disease and skin lesions. While delayed in onset and/or reduced in severity compared with TCR α+/+ MRL/lpr animals, renal and skin lesions in αβ T cell-deficient animals were clearly increased in severity compared with age-matched control non-autoimmune mice. In contrast to TCR α+/+ MRL mice, whose disease reflected pan-isotype immune complex deposition with significant complement fixation, renal disease in TCR α?/? MRL animals reflected predominantly IgG1 immune complex deposition, with poor complement fixation. Thus, this study demonstrates conclusively that non-αβ T cell-dependent mechanisms can induce renal and skin injury in murine lupus, but at least in the kidney, only via humoral autoimmunity of a relatively non-pathological isotype which results in the delayed onset of end-organ damage.     

姜黄素对MRL/lpr狼疮鼠肾组织富含脯氨酸的酪氨酸激酶2信号转导途径表达的影响

目的 探讨富含脯氨酸的酪氨酸激酶2(PYK2)信号转导途径在MRL/lpr模型鼠狼疮肾炎中所起的作用以及姜黄素对PYK2信号转导途径活化的影响.方法 选用MRL/lpr转基因狼疮鼠为研究对象,给予姜黄素干预治疗后,采用免疫组化方法研究狼疮鼠肾脏磷酸化PYK2的组织分布情况,采用Western blot方法研究磷酸化PYK2蛋白的定量表达.结果 MRL/lpr狼疮鼠肾脏的磷酸化PYK2蛋白明显活化,给予姜黄素干预治疗后肾脏的磷酸化PYK2蛋白表达降低.结论 狼疮鼠肾脏PYK2信号转导途径的活化与狼疮肾炎的发病密切相关,姜黄素可以降低PYK2信号转导途径的表达.     

Intratumoral Tcf1+PD-1+CD8+ T Cells with Stem-like Properties Promote Tumor Control in Response to Vaccination and Checkpoint Blockade Immunotherapy

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自身反应性T细胞系及克隆的建立与TCR使用情况分析

目的：体外建立可长期生长的自身反应性T细胞系克隆，并分析其T细胞受体的使用情况。方法：用狼疮小鼠BXSB自身脾脏作为刺激细胞，在体外建立长期生长的自身反应性T细胞系（ATL）通过有限稀释法进行克隆，应用锚定PCR方法分析其特异的T细胞受体应用。结果：建立了H－2^b限制性的自身反应T细胞系和2个T细胞克隆。T细胞系主要应用TRBV2S1、TRAV5S1和TRAV1021，而2个T细胞克隆均为TRBV2S1和TRAV10S1。分析其表型为CD3^ CD4^ CD28^ 。结论：从狼疮小鼠获得了自身反应性T细胞系及克隆，其T细胞受体利用具有一定的局限性。     

MRL/lpr小鼠肾组织JAK/STAT信号转导途径的表达和雷帕霉素对其表达的影响

目的 探讨JAK／STAT1信号转导途径在MRL／lpr小鼠狼疮肾炎中所起的作用以及雷帕霉素对JAK／STAT1信号转导途径活化的影响。方法采用MRL／lpr转基因鼠，给予雷帕霉素干预治疗后，采用免疫组化方法研究肾脏磷酸化STAT1的组织分布情况，采用Westernblot方法研究磷酸化STAT1蛋白的表达，采用SYBRgreen嵌合荧光法real-time定量PCR研究SOCS-1mRNA的表达，从而研究STAT1的活化水平。结果MRL/lpr狼疮鼠肾脏的磷酸化STAT1蛋白明显活化，SOCS-1基因的表达升高，给予雷帕霉素治疗后肾脏的磷酸化STAT1蛋白表达降低，SOCS-1基因的表达降低。结论JAI（／STAT1信号转导途径的活化与狼疮肾炎的发病相关，雷帕霉素可以降低JAK／STAT1信号转导途径的表达．这可能是雷帕霉素治疗系统性红斑狼疮的机理之一。     

Non-DNA-Binding Antibodies in Patients with Lupus Nephritis Could Recognize Membrane Proteins of Glomerular Mesangial Cells

Lupus nephritis (LN) is a prototypic autoimmune disease, however, the precise immuno-pathogenesis of LN remains to be elucidated. In our previous studies, autoantibodies against mesangial cells had been identified in sera from patients with lupus nephritis and could bind the membrane proteins of human mesangial cells (HMC) directly through antigen-antibody interaction without DNA bridge. The current study is to investigate whether the autoantibodies were associated with anti-DNA antibodies and their target antigens distribution in different cell types. Sera from nine patients with renal biopsy proven lupus nephritis with positive anti-dsDNA antibodies and four healthy subjects were collected. IgG was isolated by Protein G affinity chromatography and then non-DNA-binding IgG fractions were obtained after deletion of anti-DNA antibodies using a DNA-cellulose affinity column. Membrane proteins, obtained from HMC, human umbilical vein endothelial cells (HUVEC), peripheral mononuclear cells by sonication and sequential centrifugation, were solubilized and applied in Western-blot analysis to characterize the target antigens. In results, the non-DNA-binding IgG fractions from sera of patients with lupus nephritis could blot the protein(s) of HMC membrane at 74, 63, and 42 kD. However, only a similar 74-kD protein could be blotted on membrane of HUVEC, and the target antigens on membranes of mononuclear cells were heterogeneous. In conclusion, our preliminary study had demonstrated that non-DNA binding autoantibodies against mesangial cells could be found in sera from patients with lupus nephritis. Although the target antigens might not be cell specific, the roles of these autoantibodies in the pathogenesis of lupus nephritis need further investigation.