转化生长因子-β1联合白细胞介素-2体外诱导非肥胖糖尿病小鼠调节性T细胞的产生

目的 体外诱导非肥胖糖尿病(NOD)小鼠CD4+ CD25+Foxp3+调节性T细胞(Treg)的产生并检测其免疫抑制功能.探讨外源性白细胞介素(IL)-2在诱导方案中的作用.方法 分选NOD小鼠童贞T细胞(Naive T),利用Anti-CD3、Anti-CD28刺激,同时给予转化生长因子-β1(TGF-β1)和白细胞介素-2(IL-2),共同培养5 d,收获诱导性Treg(iTreg),经流式细胞仪检测其表型.利用体外T细胞增殖体系,对比NOD小鼠天然Treg(nTreg),评价iTreg的免疫抑制能力.将诱导方案中的IL-2撤除以观察其作用.结果 TGF-B1联合IL-2能诱导NOD小鼠Naive T转化为iTreg,较对照组有统计学意义[(41.33±3.21)%比(8.00±3.00)%,P《0.05].iTreg可有效抑制T细胞增殖,其能力与nTreg的差异元统计学意义[(40.33±1.03)%比(38.33±3.06),P》0.05].外源性IL-2有利于iTreg的产生[(41.33±3.21)%比(15.00±1.00)%,P《0.05].结论 TGF-β1联合IL-2可在体外诱导Naive T转化为具有免疫抑制功能的Treg.     

Persistent expansion of CD4+ effector memory T cells in Wegener's granulomatosis

In order to test the hypothesis that Wegener's granulomatosis (WG) is associated with an ongoing immune effector response, even in remission, we examined the distribution of peripheral naive and memory T-lymphocytes in this disease, and analyzed the function-related phenotypes of the memory T-cell population. Peripheral blood mononuclear cells (PBMCs) were freshly isolated from WG-patients in remission (R-WG, n=40), active WG-patients (A-WG, n=17), and age-matched healthy controls (HCs, n=21). Expression of CD4, CD8, CD45RO, CCR7, interleukin (IL)-18Ralpha, ST2L, and FoxP3 were determined by four-color flow cytometric analysis. CD45RO and CCR7 were used for distinction between naive and memory T cells, IL-18Ralpha, ST2L, and FoxP3 for the assessment of Type1, Type2, and regulatory T-cells, respectively. In R-WG, the CD4+CD45RO+CCR7- effector memory T-cell subpopulation (TEM) was relatively increased, whereas the CD4+CD45RO-CCR7+ naive T-cell population (TNaive) was decreased as compared to HC. The distribution of naive and memory CD8+T cells did not differ between R-WG, A-WG, and HC, nor did CD4+CD45RO+CCR7+ central memory T cells (TCM). In contrast to HC, the percentage of CD4+TNaive cells in R-WG correlated negatively with age, whereas CD4+TEM cells showed a positive correlation. In R-WG, a skewing towards Type2 T cells was observed in CD4+TEM cells. No differences were detected in FoxP3+CD4+TEM cells between R-WG and A-WG, whereas the FoxP3-CD4+TEM cells were increased in R-WG and decreased in A-WG as compared to HC. Collectively, peripheral blood homeostasis of CD4+T cells is disturbed in R-WG with the persistent expansion of non-regulatory CD4+TEM cells. These cells might be involved in relapse and may constitute a target for therapy.     

关节置换患者外周血调节T细胞水平变化及其临床意义

目的探讨调节性T细胞(Treg)与关节置换假体植入的关系及临床意义。方法 2009年1月至2009年6月将人工髋关节置换手术患者及同期无假体植入的关节镜手术患者分为两组,用流式细胞仪检测术前及术后3 d外周血Treg水平并进行统计学分析。结果关节置换组术前外周血中Treg的水平为(2.99±1.33),术后为(4.66±1.96),两者比较差异有统计学意义(P0.01);非假体植入组术前为(3.36±1.61),术后为(3.47±1.83),两者比较差异无统计学意义(P0.05);术后关节置换组与非假体植入组对比,两组间Treg水平的差异有统计学意义(P0.01)。结论假体植入体内可使患者外周血CD4+CD25+调节性T细胞水平显著升高,提示关节置换假体感染引起的免疫反应与单纯组织感染时的免疫反应不同,T细胞能否成为假体感染的病情进展及疗效评估的指标有待进一步研究。     

不明原因复发性流产机制中Th17细胞和CD4~+CD25~+调节性T细胞的研究进展

复发性自然流产(RSA)发病原因有多种,约有一半以上的患者发病原因不明,称之为不明原因复发性流产(URSA)。URSA与母胎免疫耐受失衡有着密切的关系。辅助性T细胞17(Th17细胞)和CD4~+CD25~+调节性T细胞(Treg细胞)是近年来新发现的免疫调节细胞。Th17细胞有很强的促炎性作用,可引起多种自身免疫性疾病。Treg细胞则有很强的免疫抑制作用,通过维持自身免疫耐受和控制自身激活的CD4~+T细胞的增殖而抑制免疫疾病的发展。在正常情况下,Th17细胞与Treg细胞的相互作用使机体效应和抑制处于一种微妙而复杂的状态。维持孕妇机体Th17/Treg平衡,对成功妊娠的维持起着重要作用。目前越来越多的研究显示,造成URSA的主要原因是由于免疫耐受遭到破坏,但其具体机制需进一步研究和探讨。本文对Th17细胞和Treg细胞在URSA流产机制中的研究进展进行综述。     

CD4+ T cells, without CD8+ or B lymphocytes, can reject xenogeneic skin grafts

Abstract: Previous experiments have shown that rejection of xenogeneic skin grafts by mice is particularly dependent on CD4⁺ T cells. There are two possible explantations for this finding: either 1) "help" provided by CD4⁺ T cells is essential for CD8⁺ T cell-, B cell-, or NK cell-mediated effector mechanisms of rejection, or 2) CD4⁺ cells are themselves responsible for rejection, perhaps by some nonspecific effector mechanism. To examine these two hypotheses, we transplanted pig skin onto SCID mice and then reconstituted the mice with selected subpopulations of lymphocytes. Mice that did not received CD4⁺ T cells were unable to reject their xenografts, whereas those receiving CD4⁺ cells could do so in the absence of CD8⁺ cells or B cells and even when additionally depleted of NK cells by treatment with anti-Asialo GM1 antibody. Additional experiments were performed both in vivo and vitro to confirm the absence in test mice of CD4⁺ or CD8⁺ and B lymphocytes, respectively. These results suggest that CD4⁺ T cells are not only necessary for rejection of xenogeneic skin grafts by mice, but that they can do so without CD8⁺ cells or B cells, and probably without NK cells. Since CD4⁺ cells in mice have been shown to recognize xenogeneic antigens indirectly, this suggests that a nonspecific effector mechanism may be involved in the rejection of xenografts. In these experiments allogeneic skin grafts behave quite differently as they could not be rejected by this mechanism.     

Differential cyclosporin-A sensitivity on survival and activation of umbilical cord and adult peripheral blood CD4+ T cells

Enhanced cyclosporine-A (CsA) sensitivity of umbilical cord blood (CB) CD4(+) T cells may contribute to the lower incidence of graft-versus-host disease (GVHD) after mismatched CB transplantation. Interleukin (IL)-15, an IL-2 like gamma-chain signaling cytokine, may bypass CsA inhibition and play an important role in GVHD pathogenesis. The present study examines CsA sensitivity of IL-15-driven CB CD4(+) T cell survival, activation and proliferation, comparing adult peripheral blood (APB) CD4(+) T cell responses. We establish that (1) resting CB CD4(+) T cells were more susceptible to CsA-induced cell death than their adult counterpart; (2) IL-15 help support the survival of resting CB CD4(+) T cell under the influence of CsA, though to a lesser degree that observed in adults; (3) higher CsA sensitivity of CD25 up-regulation following TCR activation was observed in CB but more readily counteracted by IL-15 compared to adults; (4) IL-15-driven proliferation of TCR-activated CD4(+) T cells was more susceptible to CsA inhibition than corresponding adults; and (5) TCR-activated CB CD4(+) T cells surviving high dose CsA (5 microg/ml) in IL-15-supplemented cultures expressed significantly lower percentages of CD45RO(-)/CD25(+) subsets compared to corresponding APB. Taken together, the differential CsA sensitivity and IL-15 response between CB and APB CD4(+) T cells may contribute to the lessened GVHD severity in the setting of CB transplantation.     

Suppressor function of umbilical cord blood-derived CD4+CD25+ T-regulatory cells exposed to graft-versus-host disease drugs

BACKGROUND: This study examines the effects of the most commonly used graft-versus-host disease (GVHD) prophylactic drugs on inducing apoptosis and suppressor cell function of human umbilical cord blood (UCB) CD4+25+ Treg and CD4+25- cells. METHODS: Cyclosporin A (CSA), methylprednisolone (MP), methotrexate (MTX), and mycophenolic acid (MPA) were added to the final 6 days of expansion cultures of Treg or CD4+25- T-cells isolated from the same donor and each concurrently cultured under the same conditions. Cell viability was measured for CD4+25+ as compared to CD4+25- T-cells and Treg function was assessed. The effects of these immunosuppressive drugs, Treg cells, or both also were tested in a primary allogeneic mixed lymphocyte response (MLR) response. RESULTS: The cell viability percentages were lower for CD4+25- cells than for Treg cells when MP, MTX, or MPA was added for the last 6 days of an expansion culture. Under these interleukin (IL)-2 based expansion conditions, CSA had no effect. The addition of any of the four GVHD prophylactic agents to the expansion phase of culture did not reduce the MLR suppressive capacity of Treg cells. Overall MLR suppression was increased when Treg cells were added along with CSA and MP to a primary MLR culture, whereas MTX modestly reduced Treg suppression. CONCLUSION: These data indicate a general resistance of expanded UCB Treg cells to GVHD immune suppressive agents and support trials to test UCB Treg infusions under the cover of GVHD prophylactic drugs in hematopoietic cell transplantation.     

Transplantation of human CD34+ stem cells from umbilical cord blood to rats with thioacetamide-induced liver cirrhosis

BACKGROUND: Liver fibrosis results from accumulation of extracellular matrix components and is associated with many chronic hepatic diseases. There is to date no specific therapy for this disease, and patients receive treatment for its associated complications. Specific progenitor cells, known as oval cells, are present in the liver. As oval cells express markers such as CD34, they are thought to arise from a hematopoietic precursor. The aim of this work was to investigate whether transplantation of hematopoietic CD34(+) stem cells could improve hepatic fibrosis by their differentiation into hepatocytes. METHODS: CD34(+) stem cells from human umbilical cord blood were purified, transduced with a lentiviral vector containing the green fluorescent protein (GFP) gene and injected via portal vein into rats with liver cirrhosis induced by the 4-month administration of thioacetamide. Rats were killed 15 and 60 days post-transplantation. RESULTS: Up to 37% and 22% fluorescent cells were observed in the blood of control and cirrhotic rats, respectively, at 15 days post-transplantation. At 60 days post-transplantation, however, fluorescent cells were completely absent from the blood. Fluorescence was not detected in liver sections at either 15 or 60 days post-transplantation. Polymerase chain-reaction study to detect the GFP gene ruled out silencing of the transgene. CONCLUSIONS: These results suggest that the transplanted cells did not engraft in the liver and were eliminated from the rats.     

Anti-neutrophil cytoplasmic antibodies and effector CD4+ cells play nonredundant roles in anti-myeloperoxidase crescentic glomerulonephritis

Most humans with microscopic polyarteritis and anti-myeloperoxidase (anti-MPO), anti-neutrophil cytoplasmic antibodies (ANCA) develop "pauci-immune" crescentic glomerulonephritis. For dissection of the roles of ANCA and cell-mediated effectors in microscopic polyarteritis, experimental autoimmune anti-MPO glomerulonephritis was induced by immunizing C57BL/6 mice with human MPO. Autoimmunity to mouse MPO (ANCA and CD4+ cell reactivity) was induced. Challenge with anti-glomerular basement membrane globulin resulted in accumulation of neutrophils, CD4+ cells and macrophages, and significant numbers of crescentic glomeruli compared with similarly challenged control-immunized mice. MPO-deficient (Mpo(-/-)) mice immunized with MPO developed similar immune responses to MPO but failed to recruit effector cells to glomeruli or develop significant crescent formation, suggesting that MPO is acting as a planted glomerular autoantigen. Effector CD4+ cell depletion in this model attenuated crescentic glomerulonephritis and effector cell influx without altering ANCA titers. However, B cell-deficient mice, with no ANCA, still developed severe crescentic glomerulonephritis with accumulation of effector cells. Intravital microscopy studies demonstrated that passive transfer of sera from MPO-immunized Mpo(-/-) mice to LPS-primed mice rapidly induced glomerular neutrophil accumulation and release of MPO. These studies provide in vivo evidence in a relevant vascular bed for both humoral and cellular anti-MPO responses as key inducers of injury. ANCA induces glomerular neutrophil infiltration and MPO deposition. Subsequently, anti-MPO CD4+ cells recognize MPO as a planted glomerular antigen and act with macrophages to amplify severe glomerular injury.     

成骨肉瘤患者TH1/TH2亚群漂移研究

观察成骨肉瘤患者辅助性Ｔ淋巴亚群中Ｔｈ１／Ｔｈ２亚群的变化,为细胞因子免疫治疗提供依据。方法应用放射免疫法以及酶联免疫吸附法检测成骨肉瘤患者血清中ＩＬ－２、ＩＬ－４、ＩＬ－６、ＴＮＦ－α的含量,检测外周血单个核细胞培养上清中ＩＬ－２、ＩＬ－４含量。结果成骨肉瘤血清中及培养上清中ＩＬ－２减少,而ＩＬ－４、ＩＬ－６、ＴＮＦ－α含量增加。结论成骨肉瘤患者中存在有Ｔｈ１／Ｔｈ２平衡失调,其中Ｔｈ１亚群功能抑制,Ｔｈ２亚群功能亢进,它们与肿瘤在宿主体内生长密切相关。     

人脐血CD133+血管内皮祖细胞的培养、鉴定与分化研究

目的探讨从人脐血中分离、体外培养CD133^＋血管内皮祖细胞（EPCs）的方法及其生长特性和鉴定。方法采用密度梯度离心法结合MACS分选法提取人脐血中CD133^＋细胞,进行流式细胞仪检测纯度,予EBM-2培养液接种培养,观察其生长特性;利用Dil-LDL及FITC-Lectin摄取实验、细胞免疫组织化学等进行鉴定。结果经流式细胞仪检测CD133^＋细胞平均占单核细胞的（1．13±0．10）％,磁珠分选所得CD133^＋细胞平均纯度为（91．45±1．04）％;CD133^＋细胞贴壁生长,可分化为梭形血管内皮细胞及形成集落;CD133^＋细胞培养过程中Dil-LDL及FITC-Lectin摄取阳性,双染阳性率为（95．83±1．72）％;CD133^＋细胞培养1周后经免疫组织化学检测CD34、Ⅷ因子阳性率分别为（95．83±2．23）％和（95．92±1．43）％,与人脐静脉内皮细胞比较差异无统计学意义;CD133^＋细胞体外培养4d、1周可形成小血管结构。结论免疫磁珠分选法可获取较高纯度CD133^＋血管内皮祖细胞,在生长因子作用下诱导其分化为成熟血管内皮细胞。     

探讨CD34+CD44+细胞输入量对无关脐血移植后造血恢复的影响

目的　研究用无关脐血移植治疗儿童急性白血病时 ,CD3 4 CD44 细胞输入量对中性粒细胞和血小板恢复时间的影响。方法　用流式细胞术分析复苏后的CD3 4 CD44 细胞数 ,并对 18例儿童急性白血病患者在无关脐血移植后的中性粒细胞和血小板恢复时间等进行测定。结果　 18例患者中 ,CD3 4 CD44 细胞输入量为 (5.90～ 2 97.0 2 )× 10 4 /kg(中位数 54.11× 10 4 /kg)。移植后中性粒细胞 >0 .5× 10 9/L的时间为 11～ 2 3d(中位数为 17.5d) ,血小板 >2 0× 10 9/L的时间为 12～ 118d(中位数 41d)。中性粒细胞恢复时间与CD3 4 CD44 细胞输入量存在相关性 ,γ值为 -0 .657,P <0 .0 1;血小板恢复时间与CD3 4 CD44 细胞输入量也有相关性 ,γ值为 -0 .490 ,P <0 .0 5。结论　CD3 4 CD44 细胞输入量与无关脐血移植后的造血重建有关     

Differential role of CD4+ cells in the sensitization and effector phases of accelerated graft rejection

Although CD4-targeted therapy markedly prolongs survival of organ allografts in naive rodents, its effects in primed hosts have not been studied. In our model of accelerated rejection (ACCR) of cardiac Tx in rats, treatment with BWH-4, a CD4 mAb (IgG2a), in the sensitization (between skin and heart Tx) but not in the effector (after cardiac Tx) phase, abrogated fulminant less than 36 hr rejection response and prolonged Tx survival to ca. 11 days. This effect correlated with decreased frequency of circulating CD4+ cells, but it did not depend upon their total depletion. It was also related to BWH-4 mAb-mediated elimination/depression of strong anti-donor humoral responses and cellular responses as determined by lymphocyte-mediated cytotoxicity and mixed lymphocyte reaction and mounted otherwise at the time of engraftment by untreated sensitized hosts. Immunoperoxidase studies of cardiac Tx from BWH-4-conditioned recipients revealed reduced T and B cell activities, reflected in abolition/reduction in deposition of humoral mediators, infiltrating cells, intra-Tx elaboration of interleukin-2 and interferon-gamma, and cell activation. This first report of the successful use of CD4 mAb in sensitized recipients of vascularized organ Tx, stresses the role of CD4+ cells as potential targets for immunosuppression in the sensitization phase of accelerated Tx injury. The beneficial therapeutic effect, probably due to both depletion and functional inhibition of CD4+ T cells, has been achieved by using relatively low doses of BWH-4 mAb.     

Morbidly obese human subjects have increased peripheral blood CD4+ T cells with skewing toward a Treg- and Th2-dominated phenotype

Obesity is associated with local T-cell abnormalities in adipose tissue. Systemic obesity-related abnormalities in the peripheral blood T-cell compartment are not well defined. In this study, we investigated the peripheral blood T-cell compartment of morbidly obese and lean subjects. We determined all major T-cell subpopulations via six-color flow cytometry, including CD8+ and CD4+ T cells, CD4+ T-helper (Th) subpopulations, and natural CD4+CD25+FoxP3+ T-regulatory (Treg) cells. Moreover, molecular analyses to assess thymic output, T-cell proliferation (T-cell receptor excision circle analysis), and T-cell receptor-β (TCRB) repertoire (GeneScan analysis) were performed. In addition, we determined plasma levels of proinflammatory cytokines and cytokines associated with Th subpopulations and T-cell proliferation. Morbidly obese subjects had a selective increase in peripheral blood CD4+ naive, memory, natural CD4+CD25+FoxP3+ Treg, and Th2 T cells, whereas CD8+ T cells were normal. CD4+ and CD8+ T-cell proliferation was increased, whereas the TCRB repertoire was not significantly altered. Plasma levels of cytokines CCL5 and IL-7 were elevated. CD4+ T-cell numbers correlated positively with fasting insulin levels. The peripheral blood T-cell compartment of morbidly obese subjects is characterized by increased homeostatic T-cell proliferation to which cytokines IL-7 and CCL5, among others, might contribute. This is associated with increased CD4+ T cells, with skewing toward a Treg- and Th2-dominated phenotype, suggesting a more anti-inflammatory set point.     

肝癌病人外周血中CD4+CD25+FOXP3+调节性T淋巴细胞表达水平的临床研究

目的 了解CD4+CD25+FOXP3+T调节性T细胞在肝癌病人外周血中的表达水平并探讨其临床意义.方法 应用流式细胞术测定18例肝癌病人外周血CD4+CD25+FOXP3+调节性T细胞占CD4+T淋巴细胞百分比,并与26例l临床对照者和24例健康对照者进行比较.结果 肝癌病人外周血中CD4+CD25+T细胞占CD4+T细胞百分比(4.25%±3.98%)明显高于临床对照组(1.34%±1.14%)及健康对照组(1.29%±0.95%)(P＜0.01),而两个对照组之间并无显著性差异(P＞0.05).CD4+CD25+FOXP3+T细胞在肝癌病人外周血所占CD4+T细胞比率(2.94%±0.91%)也较临床对照组(0.76%±0.34%)及健康对照组(0.81%±0.29%)显著升高(P＜0.001),且升高幅度强于CD4+CD25+T细胞水平,两个对照组之间并无显著性差异(P＞0.05).结论 CD4+CD25+FOXP3+T细胞是更为准确的调节性T细胞,其在肝癌病人外周血中表达水平明显升高,检测CD4+CD25+FOXP3+T水平对肝癌的预防治疗具有重要临床意义.     

Intrarenal antigens activate CD4+ cells via co-stimulatory signals from dendritic cells

Dendritic cells in the kidney take up antigens, but little is known about their role in providing co-stimulatory signals for the activation of CD4⁺ cells. This study examined the phenotype of dendritic cells in the renal interstitium and in the lymph node draining the kidney before and after intrarenal ovalbumin injection. After intrarenal injection of the antigen, expression of the co-stimulatory molecules CD86 and programmed cell death ligand 1 (PD-L1) increased on renal dendritic cells, whereas expression of only CD86 increased on dendritic cells of the draining lymph node. The activation and proliferation of antigen-specific CD4⁺ cells in the lymph node were assessed by transfer of naïve, fluorescently labeled ovalbumin-specific T cell receptor transgenic cells to mice before antigen administration. Blocking both CD86 and CD80 profoundly inhibited CD4⁺ cell proliferation, but CD86 was the dominant CD28 ligand in the early proliferative response of CD4⁺ cells. Conversely, activation of PD-1, the receptor expressed on CD4⁺ cells that binds PD-L1 and PD-L2, reduced the proliferation of CD4⁺ cells in the draining lymph node. Comparing subcutaneous and intrarenal administration of antigen, it was found that CD4⁺ cell activation was slower and the effects of combined CD80 and CD86 blockade were more profound when antigen was presented via the kidney compared with the skin. In summary, renal dendritic cells take up antigen and participate in the control of antigen-specific CD4⁺ cell proliferation by upregulating co-stimulatory molecules such as CD86 that stimulate CD4⁺ cell proliferation and by signaling through PD-1, which prevents an inappropriately exuberant immune response.Because CD4⁺ cells direct adaptive immune responses in infection, autoimmunity, and allogeneic responses they are relevant to renal infection, pathologic renal inflammation, and renal transplantation. CD4⁺ cells are activated in local draining lymph nodes (LN) after encounters with activated and licensed dendritic cells (DC) presenting relevant antigenic peptides. Licensed DC that have altered their phenotype in inflammation migrate from tissues to present antigen. T cells proliferate, acquire effector functions, and leave the LN several days after antigen is presented.¹ Co-stimulatory signals are important for effective immune responses, providing the “second signal” for CD4⁺ cell activation. Co-stimulatory molecules provide positive or negative signals to enhance or inhibit the immune response. Antigen presentation in the absence of co-stimulatory signals results in anergy and is important in peripheral tolerance. DC co-stimulatory molecule expression is an integral part of DC maturation and largely defines their capacity to activate naïve T cells. The B7 family of co-stimulatory molecules includes the prototypic positive signals B7-1 (CD80) and B7-2 (CD86).² Their ligands are CD28, which is constitutively expressed on CD4⁺ T cells and induces activation,³ and CTLA4 (CD152), which is expressed after T cell activation and limits T cell activation.⁴ The absence of signaling through CD28 impairs naïve CD4⁺ T cell activation.⁵The immune receptor programmed cell death 1 (PD-1) and its ligands, PD-L1 and PD-L2, B7 family members, provide negative co-stimulatory signals. They limit immune responses to avoid an overexuberant response and may prevent the development of pathogenetic self-reactivity.^2,6 PD-1–deficient mice have enhanced immune responses with autoimmunity,^7,8 and evidence is accumulating that PD-1 and its ligands regulate immune responses in peripheral tissues.⁶ Information on the role of PD-1 in the early activation of CD4⁺ T cells is limited because PD-1 expression is delayed after CD4⁺ cell activation.⁹ Expression persists on the cell surface, suggesting involvement in a later phase of CD4⁺ T cell activation, including downregulation of activated T cells. Generally speaking, PD-L2 is expressed largely by DC, whereas PD-L1 may also be expressed by tissue cells.^2,6,10Despite their central role in the immune response, CD4⁺ cells specific for an individual antigen exist at low frequency, even in active immune responses. This low frequency of antigen-specific CD4⁺ cells makes the proliferation and behavior of antigen-specific CD4⁺ cells difficult to study in vivo. The development of T cell receptor (TcR) transgenic mice in which the majority of T cells express a single TcR allows study of how immune signals induce antigen-specific responses by in vivo assessment of relatively large numbers of antigen-specific cells.^1,11 Because the skin is a primary site of entry of infectious threats and subcutaneous injection is simple, studies are performed by injecting antigen subcutaneously. The kidney, a solid internal organ, performs different functions compared with the skin. Whereas the tubulointerstitium may be exposed to foreign antigens via ascending infection, proteins processed by renal DC are more likely to be self-antigens or innocuous foreign antigens. Renal DC form a relatively extensive network in the tubulointerstitium¹² but may not be as potent at inducing T cell proliferation as splenic DC.^13,14These studies sought to define the response of renal DC exposed to antigen in the kidney parenchyma. The timing of proliferation was compared with subcutaneous antigen injection, the expression of co-stimulatory molecules and capacity to present antigen and activate antigen-specific CD4⁺ T cells in the renal draining LN was assessed, and DC co-stimulatory molecules were inhibited for better definition of the mechanisms of immune recognition and antigen presentation in the kidney. A new model of antigen presentation in the renal node was established using direct intrarenal injection and in vivo assessment of transgenic ovalbumin (OVA)-specific CD4⁺ cells. Experiments on dermal presentation of the same antigen allowed comparison of antigen presentation in the kidney with skin DC.