Different growth factor requirements for the ex vivo amplification of transplantable human cord blood cells in a NOD/SCID mouse model

The growth factor combination containing early acting cytokines FLT-3 ligand (FL), Stem Cell Factor (SCF) and thrombopoietin (TPO) is able to maintain, for an extended culture period, early stem cells, defined as long-term repopulating NOD/SCID mice (Scid Repopulating Cell-SRC) contained in cord blood (CB). In this culture system, the role of IL-6 and IL-3 has not been clearly established. Using a combination of FL+TPO+SCF with or without IL-6, we were able to form CB CD34+ cells for 30 weeks. The CB CD34+ cells cultured in this system engrafted NOD/SCID mice after 6 weeks of culture; the cells from primary recipients were also able to engraft secondary NOD/SCID mice. When CB CD34+ cells were cultured in the presence of IL-3 in the place of IL-6 we observed an even better expansion of cells and a similar clonogenic progenitor output in the first 8 weeks of culture. However, more primitive LTC-IC output increased up to week 6 with the growth factor combination containing IL-3 and then decreased and disappeared, while with the growth factor combination with or without IL-6 increased up to week 23. Cells cultured for 4 weeks with the 4-factor combination containing IL-3 engrafted NOD/SCID mice less efficiently. Repopulation of NOD/SCID mice was no longer observed when ex vivo expansion was performed for 6 weeks. This study provides some evidence that no differences could be detected in long-term maintenance and even expansion of human primitive cord blood cells cultured with FL+TPO+SCF in the presence or absence of IL-6. Under the culture conditions employed in this study, the presence of IL-3 reduced the repopulating potential of expanded CB CD34+ cells.     

B lymphocytes not required for progression from insulitis to diabetes in non-obese diabetic mice

Previous studies have implicated B lymphocytes in the pathogenesis of diabetes in the non-obese diabetic (NOD) mouse. While it is clear that B lymphocytes are necessary, it has not been clear at which stage of disease they play a role; early, late or both. To clarify when B lymphocytes are needed, T lymphocytes were transferred from 5-week-old NOD female mice to age-matched NOD/severe combined immunodeficiency (SCID) recipient mice. NOD/SCID mice, which lack functionally mature T and B lymphocytes, do not normally develop insulitis or insulin-dependent diabetes melitus (IDDM). The NOD/SCID mice that received purified T lymphocytes from 5-week-old NOD mice subsequently developed insulitis and diabetes even though they did not have detectable B lymphocytes. This suggests that while B lymphocytes may be essential for an initial priming event they are not requisite for disease progression in the NOD mouse.     

Mechanisms of accelerated immune-mediated diabetes resulting from islet beta cell expression of a Fas ligand transgene

Nonobese diabetic (NOD) mice transgenic for Fas ligand (FasL) on islet beta cells (HIPFasL mice) exhibit an accelerated diabetes distinct from the normal autoimmune diabetes of NOD mice. This study was undertaken to define the mechanism underlying accelerated diabetes development in HIPFasL mice. It was found that diabetes in HIPFasL mice is dependent on the NOD genetic background, as HIPFasL does not cause diabetes when crossed into other mice strains and is lymphocyte dependent, as it does not develop in HIPFasL(SCID) mice. Diabetes development in NOD(SCID) recipients of diabetic HIPFasL splenocytes is slower than when using splenocytes from diabetic NOD mice. Beta cells from HIPFasL mice are more susceptible to cytokine-induced apoptosis than wild-type NOD beta cells, and this can be blocked with anti-FasL Ab. HIPFasL islets are more rapidly destroyed than wild-type islets when transplanted into nondiabetic NOD mice. This confirms that FasL(+) islets do not obtain immune privilege, and instead NOD beta cells constitutively expressing FasL are more susceptible to apoptosis induced by Fas-FasL interaction. These findings are consistent with the accelerated diabetes of young HIPFasL mice being a different disease process from the autoimmune diabetes of wild-type NOD mice. The data support a mechanism by which cytokines produced by the insulitis lesion mediate up-regulation of beta cell Fas expression, resulting in suicide or fratricide of HIPFasL beta cells that overexpress FasL.     

Regulation of diabetes development by regulatory T cells in pancreatic islet antigen-specific TCR transgenic nonobese diabetic mice

Nonobese diabetic (NOD) mice carrying a transgenic TCR from an islet Ag-specific CD4 T cell clone, BDC2.5, do not develop diabetes. In contrast, the same transgenic NOD mice on the SCID background develop diabetes within 4 wk after birth. Using a newly developed mAb specific for the BDC2.5 TCR, we examined the interaction between diabetogenic T cells and regulatory T cells in NOD.BDC transgenic mice. CD4 T cells from NOD.BDC mice, expressing high levels of the clonotype, transfer diabetes to NOD.SCID recipients. In contrast, CD4 T cells expressing low levels due to the expression of both transgenic and endogenous TCR alpha-chains inhibit diabetes transfer. The clonotype-low CD4 T cells appear late in the ontogeny in the thymus and peripheral lymphoid organs, coinciding with resistance to cyclophosphamide-induced diabetes. These results demonstrate that diabetic processes in NOD.BDC mice are regulated by a balance between diabetogenic T cells and regulatory T cells. In the absence of specific manipulation, regulatory T cell function seems to be dominant and mice remain diabetes free. Understanding of mechanisms by which regulatory T cells inhibit diabetogenic processes would provide means to prevent diabetes development in high-risk human populations.     

NOD/SCID小鼠模型在实验血液学研究中的应用

NOD/SCID（非肥胖糖尿病/重症联合免疫缺陷）小鼠是在SCID（重症联合免疫缺陷）小鼠的基础上与非肥胖性糖尿病小鼠（NOD/Lt）品系回交的免疫缺陷鼠。NOD/SCID小鼠既有先天免疫缺陷,又有T和B淋巴细胞缺乏,各种肿瘤细胞可以植入,且较少发生排斥反应及移植物抗宿主病（GVHD）,所以NOD/SCID小鼠逐渐成为血液学实验研究的有用工具。本文从NOD/SCID小鼠的生物学特性、建立人类白血病模型、干细胞移植、药物研究及NOD/SCID小鼠应用中存在的不足和改良等方面综合述评。     

CD4+CD25+ regulatory T cells control the progression from periinsulitis to destructive insulitis in murine autoimmune diabetes

Non-obese diabetic (NOD) mice develop spontaneous T-cell responses against pancreatic beta-cells, leading to islet cell destruction and diabetes. Despite high genetic similarity, non-obese resistant (NOR) mice do not develop diabetes. We show here that spleen cells of both NOD and NOR mice respond to the islet cell antigen glutamic acid decarboxylase-65 in IFN-gamma-ELISPOT assays. Moreover, NOR-T cells induce periinsulitis in NOD SCID recipient mice. Thus, a potentially pathogenic islet cell-specific T-cell response arises in NOR and NOD mice alike; the mechanism that prevents the autoimmune progression of self-reactive T cells in NOR mice presumably acts at the level of effector function. Consistent with this hypothesis, CD4+CD25+ cell-depleted spleen cells from NOR mice mediated islet cell destruction and overt diabetes in NOD SCID mice. Therefore, islet cell-specific effector cells in NOR mice appear to be under the control of CD4+CD25+ regulatory T cells, confirming the importance of regulatory cells in the control of autoimmune diabetes.     

Cytokine-mediated deployment of SDF-1 induces revascularization through recruitment of CXCR4+ hemangiocytes

The mechanisms through which hematopoietic cytokines accelerate revascularization are unknown. Here, we show that the magnitude of cytokine-mediated release of SDF-1 from platelets and the recruitment of nonendothelial CXCR4+ VEGFR1+ hematopoietic progenitors, 'hemangiocytes,' constitute the major determinant of revascularization. Soluble Kit-ligand (sKitL), thrombopoietin (TPO, encoded by Thpo) and, to a lesser extent, erythropoietin (EPO) and granulocyte-macrophage colony-stimulating factor (GM-CSF) induced the release of SDF-1 from platelets, enhancing neovascularization through mobilization of CXCR4+ VEGFR1+ hemangiocytes. Although revascularization of ischemic hindlimbs was partially diminished in mice deficient in both GM-CSF and G-CSF (Csf2-/- Csf3-/-), profound impairment in neovascularization was detected in sKitL-deficient Mmp9-/- as well as thrombocytopenic Thpo-/- and TPO receptor-deficient (Mpl-/-) mice. SDF-1-mediated mobilization and incorporation of hemangiocytes into ischemic limbs were impaired in Thpo-/-, Mpl-/- and Mmp9-/- mice. Transplantation of CXCR4+ VEGFR1+ hemangiocytes into Mmp9-/- mice restored revascularization, whereas inhibition of CXCR4 abrogated cytokine- and VEGF-A-mediated mobilization of CXCR4+ VEGFR1+ cells and suppressed angiogenesis. In conclusion, hematopoietic cytokines, through graded deployment of SDF-1 from platelets, support mobilization and recruitment of CXCR4+ VEGFR1+ hemangiocytes, whereas VEGFR1 is essential for their angiogenic competency for augmenting revascularization. Delivery of SDF-1 may be effective in restoring angiogenesis in individuals with vasculopathies.     

Cyclin-dependent kinase 4 hyperactivity promotes autoreactivity in the immune system but protects pancreatic cell mass from autoimmune destruction in the nonobese diabetic mouse model

Cyclin-dependent kinase 4 (Cdk4) plays a central role in perinatal pancreatic beta cell replication, thus becoming a potential target for therapeutics in autoimmune diabetes. Its hyperactive form, Cdk4R24C, causes beta cell hyperplasia without promoting hypoglycemia in a nonautoimmune-prone mouse strain. In this study, we explore whether beta cell hyperproliferation induced by the Cdk4R24C mutation balances the autoimmune attack against beta cells inherent to the NOD genetic background. To this end, we backcrossed the Cdk4R24C knockin mice, which have the Cdk4 gene replaced by the Cdk4R24C mutated form, onto the NOD genetic background. In this study, we show that NOD/Cdk4R24C knockin mice exhibit exacerbated diabetes and insulitis, and that this exacerbated diabetic phenotype is solely due to the hyperactivity of the NOD/Cdk4R24C immune repertoire. Thus, NOD/Cdk4R24C splenocytes confer exacerbated diabetes when adoptively transferred into NOD/SCID recipients, compared with NOD/wild-type (WT) donor splenocytes. Accordingly, NOD/Cdk4R24C splenocytes show increased basal proliferation and higher activation markers expression compared with NOD/WT splenocytes. However, to eliminate the effect of the Cdk4R24C mutation specifically in the lymphocyte compartment, we introduced this mutation into NOD/SCID mice. NOD/SCID/Cdk4R24C knockin mice develop beta cell hyperplasia spontaneously. Furthermore, NOD/SCID/Cdk4R24C knockin females that have been adoptively transferred with NOD/WT splenocytes are more resistant to autoimmunity than NOD/SCID WT female. Thus, the Cdk4R24C mutation opens two avenues in the NOD model: when expressed specifically in beta cells, it provides a new potential strategy for beta cell regeneration in autoimmune diabetes, but its expression in the immune repertoire exacerbates autoimmunity.     

Thrombopoietin and the c-Mpl receptor: insights from gene targeting

The availability of thrombopoietin (TPO) in recombinant form has revolutionized the study of megakaryocytopoiesis and provided an exciting new reagent for clinical evaluation. Through the application of gene targeting technology, the production of mice lacking TPO or its receptor c-Mpl has provided valuable insights into the physiological roles of TPO signalling. The near identical phenotype of c-mpl-/- and TPO-/- mice provides strong biological evidence that TPO is the sole c-Mpl ligand and uses no other additional receptor itself. TPO-/- and mpl-/- mice are severely thrombocytopenic indicating that TPO is the primary physiological regulator of platelet production in vivo. The physiological basis for this platelet deficiency has been further defined by analysis of megakaryocytes and committed progenitor cells, the numbers of which are also reduced in these mutants. The platelets that are produced in the absence of TPO signalling are morphologically and functionally normal and residual production is sufficient to prevent bleeding and allow a normal lifespan. Thus, TPO-/- and mpl-/- mice also reveal that important TPO-independent mechanisms exist that control platelet production in vivo, and these mice are ideal models to explore the nature of these alternative regulators. The mechanisms regulating the circulating levels of TPO have also been elucidated in these mice, highlighting the central role of c-Mpl mediated internalisation and degradation. The unexpected observation that progenitor cells of all hemopoietic lineages are produced in reduced numbers in TPO-/- and mpl-/- mice has also led to studies that uncovered a central role for TPO signalling in hemopoietic stem cell regulation.     

Intrahepatic transplantation of CD34+ cord blood stem cells into newborn and adult NOD/SCID mice induce differential organ engraftment

In vivo studies concerning the function of human hematopoietic stem cells (HSC) are limited by relatively low levels of engraftment and the failure of the engrafted HSC preparations to differentiate into functional immune cells after systemic application. In the present paper we describe the effect of intrahepatically transplanted CD34⁺ cells from cord blood into the liver of newborn or adult NOD/SCID mice on organ engraftment and differentiation.Analyzing the short and long term time dependency of human cell recruitment into mouse organs after cell transplantation in the liver of newborn and adult NOD/SCID mice by RT-PCR and FACS analysis, a significantly high engraftment was found after transplantation into liver of newborn NOD/SCID mice compared to adult mice, with the highest level of 35% human cells in bone marrow and 4.9% human cells in spleen at day 70. These human cells showed CD19 B-cell, CD34 and CD38 hematopoietic and CD33 myeloid cell differentiation, but lacked any T-cell differentiation. HSC transplantation into liver of adult NOD/SCID mice resulted in minor recruitment of human cells from mouse liver to other mouse organs. The results indicate the usefulness of the intrahepatic application route into the liver of newborn NOD/SCID mice for the investigation of hematopoietic differentiation potential of CD34⁺ cord blood stem cell preparations.     

人T细胞急性淋巴细胞白血病小鼠动物模型的建立

目的:通过建立一理想的动物模型来模拟T细胞急性淋巴细胞白血病的发病状态,为探索急性淋巴细胞白血病全新的治疗方法提供平台。方法:采用抗鼠-CD122抗体注射NOD/SCID小鼠进行预处理,通过尾静脉注射9例不同病例的白血病细胞,以及1株T-ALL细胞系。通过检测小鼠体内白血病细胞及脏器白血病细胞浸润情况,观察白血病细胞植入。将白血病细胞进行二次移植,观察移植稳定性。对白血病动物模型进行药物处理,观察小鼠生存期,模拟人体治疗反应。结果:有4例病例的细胞及T-ALL细胞株成功植入。流式细胞检测显示受体小鼠体内较多比例人CD45+细胞表达,免疫组化显示CD45+细胞浸润小鼠不同脏器,系列移植也获得成功。体内药物处理显示地塞米松能延长小鼠的生存期,与临床观察相一致。结论:成功建立经抗鼠CD122单抗预处理的人T细胞急性淋巴细胞白血病NOD/SCID小鼠模型,具有原发疾病的所有主要特征。     

Generation of transgenic mice on an NOD/SCID background using the conventional microinjection technique

Humanized mice, which refers to immunodeficient mice repopulated with the human immune system, are powerful tools for study in the field of immunology. It has been difficult, however, to generate these transgenic (Tg) mice directly from such strains as the NOD/SCID mouse. In this study, we describe a method developed by us for the generation of Tg mice on an NOD/SCID background. First, we obtained fertilized eggs efficiently by means of in vitro fertilization (IVF); then, we attempted to generate CAG-EGFP Tg mice on an NOD/SCID background, finding that delayed timing of the microinjection after the IVF improved the time to development of the two-cell-stage embryos and the obtainment of newborns. We successfully generated Tg mice and confirmed the germ-line transmission in the offspring. In conclusion, we established a novel system for directly generating transgenic mice on an NOD/SCID background. This novel system is expected to allow improved efficiency of the generation of humanized mice.     

Humanized mice mount specific adaptive and innate immune responses to EBV and TSST-1

Here we show that transplantation of autologous human hematopoietic fetal liver CD34+ cells into NOD/SCID mice previously implanted with human fetal thymic and liver tissues results in long-term, systemic human T-cell homeostasis. In addition, these mice show systemic repopulation with human B cells, monocytes and macrophages, and dendritic cells (DCs). T cells in these mice generate human major histocompatibility complex class I- and class II-restricted adaptive immune responses to Epstein-Barr virus (EBV) infection and are activated by human DCs to mount a potent T-cell immune response to superantigens. Administration of the superantigen toxic shock syndrome toxin 1 (TSST-1) results in the specific systemic expansion of human Vbeta2+ T cells, release of human proinflammatory cytokines and localized, specific activation and maturation of human CD11c+ dendritic cells. This represents the first demonstration of long-term systemic human T-cell reconstitution in vivo allowing for the manifestation of the differential response by human DCs to TSST-1.     

Roles of salivary components in Streptococcus mutans colonization in a new animal model using NOD/SCID.e2f1-/- mice

Streptococcus mutans plays an important role in biofilm formation on the tooth surface and is the primary causative agent of dental caries. The binding of S. mutans to the salivary pellicle is of considerable etiologic significance and is important in biofilm development. Recently, we produced NOD/SCID.e2f1(-/-) mice that show hyposalivation, lower salivary antibody, and an extended life span compared to the parent strain: NOD.e2f1(-/-). In this study we used NOD/SCID.e2f1(-/-) 4 or 6 mice to determine the roles of several salivary components in S. mutans colonization in vivo. S. mutans colonization in NOD/SCID.e2f1(-/-) mice was significantly increased when mice were pre-treated with human saliva or commercial salivary components. Interestingly, pre-treatment with secretory IgA (sIgA) at physiological concentrations promoted significant colonization of S. mutans compared with sIgA at higher concentrations, or with human saliva or other components. Our data suggest the principal effects of specific sIgA on S. mutans occur during S. mutans colonization, where the appropriate concentration of specific sIgA may serve as an anti-microbial agent, agglutinin, or an adherence receptor to surface antigens. Further, specific sIgA supported biofilm formation when the mice were supplied 1% sucrose water and a non-sucrose diet. The data suggests that there are multiple effects exerted by sIgA in S. mutans colonization, with synergistic effects evident under the condition of sIgA and limited nutrients on colonization in NOD/SCID.e2f1(-/-) mice. This is a new animal model that can be used to assess prevention methods for dental biofilm-dependent diseases such as dental caries.     

NOD/LtSz-Rag1null mice: an immunodeficient and radioresistant model for engraftment of human hematolymphoid cells, HIV infection, and adoptive transfer of NOD mouse diabetogenic T cells

Development of a small animal model for the in vivo study of human immunity and infectious disease remains an important goal, particularly for investigations of HIV vaccine development. NOD/Lt mice homozygous for the severe combined immunodeficiency (Prkdcscid) mutation readily support engraftment with high levels of human hematolymphoid cells. However, NOD/LtSz-scid mice are highly radiosensitive, have short life spans, and a small number develop functional lymphocytes with age. To overcome these limitations, we have backcrossed the null allele of the recombination-activating gene (Rag1) for 10 generations onto the NOD/LtSz strain background. Mice deficient in RAG1 activity are unable to initiate V(D)J recombination in Ig and TCR genes and lack functional T and B lymphocytes. NOD/LtSz-Rag1null mice have an increased mean life span compared with NOD/LtSz-scid mice due to a later onset of lymphoma development, are radioresistant, and lack serum Ig throughout life. NOD/LtSz-Rag1null mice were devoid of mature T or B cells. Cytotoxic assays demonstrated low NK cell activity. NOD/LtSz-Rag1null mice supported high levels of engraftment with human lymphoid cells and human hemopoietic stem cells. The engrafted human T cells were readily infected with HIV. Finally, NOD/LtSz-Rag1null recipients of adoptively transferred spleen cells from diabetic NOD/Lt+/+ mice rapidly developed diabetes. These data demonstrate the advantages of NOD/LtSz-Rag1null mice as a radiation and lymphoma-resistant model for long-term analyses of engrafted human hematolymphoid cells or diabetogenic NOD lymphoid cells.     

Retention of human bone marrow-derived cells in murine lungs following bleomycin-induced lung injury

We studied the capacity of adult human bone marrow-derived cells (BMDC) to incorporate into distal lung of immunodeficient mice following lung injury. Immunodeficient NOD/SCID and NOD/SCID/beta(2) microglobulin (beta(2)M)(null) mice were administered bleomycin (bleo) or saline intranasally. One, 2, 3 and 4 days after bleo or saline, human BMDC labeled with CellTracker Green CMFDA (5-chloromethylfluorescein diacetate) were infused intravenously. Retention of CMFDA(+) cells was maximal when delivered 4 days after bleo treatment. Seven days after bleo, <0.005% of enzymatically dispersed lung cells from NOD/SCID mice were CMFDA(+), which increased 10- to 100-fold in NOD/SCID/beta(2)M(null) mice. Preincubation of BMDC with Diprotin A, a reversible inhibitor of CD26 peptidase activity that enhances the stromal-derived factor-1 (SDF-1/CXCL12)/CXCR4 axis, resulted in a 30% increase in the percentage of CMFDA(+) cells retained in the lung. These data indicate that human BMDC can be identified in lungs of mice following injury, albeit at low levels, and this may be modestly enhanced by manipulation of the SDF-1/CXCR4 axis. Given the overall low number of human cells detected, methods to increase homing and retention of adult BMDC, and consideration of other stem cell populations, will likely be required to facilitate engraftment in the treatment of lung injury.     

Role of the distal half of the c-Mpl intracellular domain in control of platelet production by thrombopoietin in vivo

The cytokine thrombopoietin (TPO) controls the formation of megakaryocytes and platelets from hematopoietic stem cells. TPO exerts its effect through activation of the c-Mpl receptor and of multiple downstream signal transduction pathways. While the membrane-proximal half of the cytoplasmic domain appears to be required for the activation of signaling molecules that drive proliferation, the distal half and activation of the mitogen-activated protein kinase pathway have been implicated in mediating megakaryocyte maturation in vitro. To investigate the contribution of these two regions of c-Mpl and the signaling pathways they direct in mediating the function of TPO in vivo, we used a knock-in (KI) approach to delete the carboxy-terminal 60 amino acids of the c-Mpl receptor intracellular domain. Mice lacking the C-terminal 60 amino acids of c-Mpl (Delta60 mice) have normal platelet and megakaryocyte counts compared to wild-type mice. Furthermore, platelets in the KI mice are functionally normal, indicating that activation of signaling pathways connected to the C-terminal half of the receptor is not required for megakaryocyte differentiation or platelet production. However, Delta60 mice have an impaired response to exogenous TPO stimulation and display slower recovery from myelosuppressive treatment, suggesting that combinatorial signaling by both ends of the receptor intracellular domain is necessary for an appropriate acute response to TPO.     

Valproic acid affects the engraftment of TPO-expanded cord blood cells in NOD/SCID mice

Hematopoietic stem and progenitor cells (HSPC) can improve the long-term outcome of transplanted individuals and reduce the relapse rate. Valproic acid (VPA), an inhibitor of histone deacetylase, when combined with different cytokine cocktails, induces the expansion of CD34+ cell populations derived from cord blood (CB) and other sources. We evaluated the effect of VPA, in combination with thrombopoietin (TPO), on the viability and expansion of CB-HSPCs and on short- and long-term engraftability in the NOD/SCID mouse model. In vitro, VPA+TPO inhibited HSPC differentiation and preserved the CD34+ cell fraction; the self-renewal of the CD34+ TPO+VPA-treated cells was suggested by the increased replating efficiency. In vivo, short- and long-term engraftment was determined after 6 and 20 weeks. After 6 weeks, the median chimerism percentage was 13.0% in mice transplanted with TPO-treated cells and only 1.4% in those transplanted with TPO+VPA-treated cells. By contrast, after 20 weeks, the engraftment induced by the TPO+VPA-treated cells was three times more effective than that induced by TPO alone, and over ten times more effective compared to the short-term engraftment induced by the TPO+VPA-treated cells. The in vivo results are consistent with the higher secondary plating efficiency of the TPO+VPA-treated cells in vitro.     

Intrahepatically transplanted human cord blood cells reduce SW480 tumor growth in the presence of bispecific EpCAM/CD3 antibody

Humanized mice were generated in order to investigate the anti-tumor efficacy of bispecific antibodies. The engraftment, distribution and differentiation of mononuclear cells (MNC) from cord blood transplanted into the liver of newborn non-obese diabetic/severe combined immunodeficiency (NOD/SCID) mice were measured. Using a human-specific polymerase chain reaction (PCR), human cells were found to be present in the liver for a time range from 5 min to 5 days. After long-term engraftment of 42 days, the highest level of human cells was measured in mouse thymus, with lower levels in spleen and bone marrow. Engrafted human cells in mouse organs showed T-cell differentiation only, as measured by CD3, CD4 and CD8 expression. The MNC transplanted intrahepatically into newborn mice were tested for T-cell mediated anti-tumor activity in vivo against subcutaneously transplanted human SW480 colon carcinoma in NOD/SCID mice. A delay of SW480 tumor growth in mice in the presence of a bispecific epithelial cell-adhesion molecule (EpCAM)/CD3 antibody was found to be associated with the presence of immunoreactive human CD3 cells within the SW480 tumor. Our data provide evidence that the intrahepatic transplantation of cord blood stem cells into newborn mice represents a valuable model for establishing functionally active human T cells with anti-tumor activity.