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EMBRYONIC STEM CELLS-CHARACTERIZATION SERIES |
a Department of Genetics, Silberman Institute of Life Sciences, The Hebrew University, Jerusalem, Israel;
b Department of Immunology, Weizmann Institute of Science, Rehovot, Israel;
c The Lautenberg Center for General and Tumor Immunology, Hadassah Medical School, The Hebrew University, Jerusalem, Israel
Key Words. Human embryonic stem cells • Peripheral blood mononuclear cells • Embryoid bodies • Cytotoxic T lymphocytes
Correspondence: Micha Drukker, Ph.D., Department of Genetics, Silberman Institute of Life Sciences, The Hebrew University, 91904 Jerusalem, Israel. Telephone: 972-2-6585183; Fax: 972-2-6584972; e-mail: dmicha{at}mail.ls.huji.ac.il
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ABSTRACT |
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INTRODUCTION |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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The first attempts to determine the antigenicity (capacity to present antigens) of very early human embryonic cells were carried out in blastocysts. Using anti–major histocompatibility complex (MHC) antibodies, a weak expression of MHC class I (MHC-I) molecules on the inner cell mass (ICM) was noted [22]. We have previously addressed this issue by examining the expression of MHC antigens in hESCs, in embryoid bodies (EBs), and in hESC-induced teratomas [23]. We found that undifferentiated cells express low levels of MHC-I molecules, which were elevated in EBs and even to a higher extent in teratomas. MHC class II (MHC-II) molecules, however, were not expressed under these conditions. Importantly, we found that the undifferentiated as well as the differentiated cells up-regulate MHC-I cell-surface expression by at least 10-fold in response to interferons (IFNs), although MHC-II expression was not induced. Although hESCs express relatively low levels of MHC-I, we could show that they are insensitive to human natural killer (NK) cell-mediated cytotoxicity [23]. However, the actual capacity of human T cells to recognize and attack hESCs and their differentiated derivatives has remained unknown.
Similar to their central role in pathogen removal, the successful engagement of antigen-presenting cells (APCs) and T lymphocytes has a pivotal role in the development of immune response toward an allograft (HLA-mismatched transplant). It is widely accepted today that after transplantation, donor-derived APCs (especially dendritic cells) emigrate to regional lymph nodes, where they encounter and stimulate naive or memory allospecific host T cells to proliferate. Central to this process are the costimulatory molecules B7.1 (CD80) and B7.2 (CD86) that promote clonal expansion of T cells and their differentiation into effector cells, which can attack the graft upon return to circulation [24]. In contrast, immunosuppressive signals such as Fas ligand (FasL, CD95L) can limit alloresponsiveness toward foreign grafts by activating the Fas receptor (CD95) in lymphocytes [25]. For instance, it was recently suggested that FasL may protect rat embryonic stem cell-like cells (RESCs) from rejection in allogeneic rat hosts [26].
In this study, by using immunocompetent mice and mouse strains with different types of immunodeficiency, we attempted to define a precise mechanism of hESC xenorejection. To determine the human T cell alloresponse toward undifferentiated as well as differentiated hESCs in vivo and in vitro, we used the human/mouse Trimera model and a primary human cytotoxic T cell (CTL) line, respectively. Furthermore, we evaluated the capacity of the hESC-derived transplants to activate immune rejection using quantitative molecular analysis methods.
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MATERIALS AND METHODS |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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CB6F1 mouse chimeras were generated. Briefly, CB6F1 mice (Harlan Olac, Oxon, U.K., http://www.harlan.com) were exposed to split-dose total body irradiation. Irradiated mice were radioprotected with bone marrow cells from nonobese diabetic severe combined immunodeficient (NOD/SCID) mice (Weizmann Institute Animal Breeding Center, Rehovot, Israel, http://www.weizmann.ac.il). One to 3 days later, approximately 100 x 106 human peripheral blood mononuclear cells (PBMCs) were injected intraperitoneally to reconstitute human T, B, and NK cell populations. The engraftment of human lymphocytes was confirmed as described [27]. Immunization was carried out 1 week before transplantation by IP injection of approximately 5 x 106 irradiated target cells. Target cells or tissues were transplanted under the kidney capsule. Transplantation to immunocompetent (BALB/c, C57Bl, SJL, and CB6F1) and immunodeficient (NOD/SCID, C57BL/6J-Lystbg, Balb-nude, and CBA/CaHN Btkxid) animals was carried out in 10- to 12-week-old mice (Jackson Laboratory, Bar Harbor, ME, http://www.jax.org).
Transplantation Procedures
All operations were performed under general anesthesia (2.5% Avertin in phosphate-buffered saline [PBS], 10 ml/kg). Host kidney was exposed through a left lateral incision. A 1.5-mm incision was made at the caudal end of the kidney capsule, and approximately 1 x 106 cells suspended in 50 to 100 µl PBS were injected using lacrimal cannula (catalog no. G-15161, Geuder, Heidelberg, Germany, http://www.geuder.de). Alternatively, 1- to 2-mm-diameter tissue fragments were grafted under the kidney capsule.
Transplant Growth and Differentiation
Animals receiving implants were euthanized 3 to 5 weeks after transplantation, and their kidneys were then removed and fixed in 10% formaldehyde. Transplants were sectioned, mounted on slides coated with poly-L-lysine, and stained by hematoxylin and eosin (H&E).
Immunohistochemical and Immunocytometry Staining
hESCs and their differentiated derivatives were trypsinized for fluorescence-activated cell sorter (FACS) analysis and stained with W6/32 and BBM1 monoclonal antibodies (mAbs) as previously described [23]. CD80 and CD86 antigens were detected by DAL-1 (immunoglobulin G1 [IgG1]) FITC-conjugated and B-T7 (IgG1) phycoerythrin (PE)-conjugated mAbs, respectively. FITC- and PE-conjugated MCG1 mAb clone was used as isotype control (IQ Products, Groningen, The Netherlands, http://www.iqproducts.nl). BB7.2 mAb (Serotec, Oxford, U.K., http://www.serotec.com) was used to verify the previously reported HLA-A2 isotype of hESC lines H9 and H13 [23]. Human specific NOK-1 mAb (ebioscience, San Diego, CA, http://www.ebioscience.com) was used for FasL detection. FITC-conjugated goat F(ab') fragment (MP Biomedicals, Aurora, OH, http://www.mpbio.com) was used as a secondary antibody.
Determination of human T cell infiltration in tumors and tissues was performed using mouse anti-human CD3 and CD45 antibodies (DakoCytomation, Glostrup, Denmark, http://www.dakocytomation.com) on paraffin-embedded sections. Horse-radish peroxidase-conjugated anti-mouse EnVision System (DakoCytomation) was used to detect the primary antibody.
Cells, Tissues, and Viruses
hESCs and teratoma cell lines were cultured and treated with interferon (IFN)-
as previously described [23, 28]. Teratoma subclones were obtained from a 4-week-old hESC-induced teratoma. Class I MHC-negative human cell line 721.221, HLA-A2, and Cw3 transfectants [29], Burkitt’s lymphoma cells (Raji), and KFL9 [30] cells (kindly provided by Dr. David Kaplan) were cultured in RPMI-1640 medium, supplemented with 10% heat-inactivated fetal calf serum (Gibco, Grand Island, NY, http://www.invitrogen.com). Skin grafts were obtained from healthy individuals undergoing cosmetic surgery. The influenza A/Sydney (A/Sydney/5/97-like [H3N2]) was propagated as previously described [31]. The cells were infected by incubating 1 x 106 cells overnight in 3 ml complete medium at 37°C and 5% CO2 with 100 µl of virus preparation.
Peptides
Influenza-A-matrix (IV/A) peptide GILGFVFTL was assembled by conventional solid-phase synthesis using an ABIMED AMS-422 automated solid-phase multiple-peptide synthesizer (Abimed, Langenfeld, Germany, http://www.abimed.de) on a 25-µmol scale. Fmoc strategy was used throughout the peptide chain assembly following the company’s protocol. All protected amino acids, coupling reagents, and polymers were obtained from Nova Biochemicals (Novabiochem, Laufelfingen, Switzerland, http://www.emdbiosciences.com). Synthesis-grade solvents were obtained from Labscan (Dublin, Ireland, http://www.labscan.ie).
Peptide Loading on Acid-Stripped Cells
Modifying a previously published protocol [32], 1 x 106 suspension cultured cells or trypsinized adherent cultured cells were pelleted and treated with 50 µl of 1% bovine serum albumin (Amresco, Solon, OH, http://www.amrescoinc.com), 300 mM Glycine (Sigma-Aldrich, St. Louis, http://www.sigmaaldrich.com) at pH 2.4. After incubation at room temperature for 90 seconds, the suspension was neutralized by adding 5 ml of RPMI 1640 medium and centrifuged at 500g. Acid-stripped cells were resuspended in 1 ml RPMI 1640 containing 2.5 µg recombinant human ß2m (BD PharMingen, San Diego, http://www.bdbiosciences.com/pharmingen) and 50 µl influenza-A-matrix (IV/A) peptide GILGFVFTL solubilized in 100% dimethylsulfoxide (Merck, Hohenbrunn, Germany, http://www.merck.com) at a concentration of 1 mg/ml. Control cells were treated identically but with no peptide. The suspensions were left in 37°C incubator for 1.5 hours, washed in 10 ml PBS, and incubated with effector PBMCs.
Production of Cytotoxic Cells and Assay
To prepare HLA-A2-restricted CTL line specific for nonameric peptide 58–66 (GILGFVFTL) derived from the influenza virus matrix A protein, 2 x 106 PBMCs from an HLA-A2+ donor were separated on Ficoll-Paque (Amersham Biosciences, Uppsala, Sweden, http://www.amersham.com) and incubated in 1 ml RPMI 1640 plus 10% human serum (Sigma-Aldrich) in the presence of 50 µM peptide. After 1 hour, the cells were washed, irradiated at 5,000 rad, and mixed with equal number of untreated PBMCs (responders) at a final concentration of 2 x 106 PBMCs in RPMI 1640 medium supplemented with human serum. Seven days later, the cells were resuspended in the same medium with 2.5 U/ml recombinant human interleukin-2 to induce T cell proliferation (Roche Diagnostics, Mannheim, Germany, https://www.roche-applied-science.com). After an additional 7 days, the cytotoxic activity of the CTL line was tested against 721.221/HLA-A2 and 721.221/Cw3 in the presence and absence of IV/A peptide. Cultures that specifically lysed at least 40% of peptide-pulsed cells and less than 10% of nonpulsed cells were maintained for future experiments.
To measure cell lysis against various target cells, the cells were labeled overnight with 1 µCi 35S methionine (Amersham Biosciences) per 1 x 106 cells. Effector cells were mixed with labeled target cells at different effector-to-target cell ratios (E/T) in U-bottomed microtiter plates. Assays were terminated by centrifugation at 1,000 rpm for 10 minutes at 4°C, and 100 µl of the supernatant was collected for liquid scintillation counting. Specific lysis was calculated as follows: % lysis = (cpm experimental well – cpm spontaneous release)/(cpm maximal release – cpm spontaneous release) x 100. Spontaneous release was determined by incubation of each group of labeled target cells with medium. Maximal release was determined by solubilizing target cells in 0.1 M NaOH. Each experiment was repeated three times. Each point represents the average of duplicate values. Error was <5% of the mean of the duplicates.
DNA Microarray Analysis
Total RNA was extracted from populations of undifferentiated and differentiated cell derivatives of the H9 hESC line. RNA extraction, hybridization to the U133A DNA microarrays, washing, and scanning were performed according to the manufacturer’s protocols (Affymetrix, Santa Clara, CA, http://www.affymetrix.com). The fluorescent signal was translated to expression value using the Affymetrix MAS5 program. All data were normalized to a mean of 1 and then log-transformed (using log base 2). DNA microarray data obtained from undifferentiated hESCs and 2-, 10-, and 30-day-old EBs and 4-week-old induced teratomas (two to three replicas each) were compared with gene expression profiles of five normal bone marrow samples, three samples of sorted CD34+ cells [33], and two samples of CD56+ NK cells (GSM18875
[NCBI GEO]
, GSM18876
[NCBI GEO]
), CD4+ T cells (GSM18877
[NCBI GEO]
, GSM18878
[NCBI GEO]
), CD8+ T cells (GSM18879
[NCBI GEO]
, GSM18880
[NCBI GEO]
), CD14 monocytes (GSM18871
[NCBI GEO]
, GSM18872
[NCBI GEO]
), CD33 myeloid cells (GSM18869
[NCBI GEO]
, GSM18870
[NCBI GEO]
), BDCA4+ dendritic cells (GSM18873
[NCBI GEO]
, GSM18874
[NCBI GEO]
), whole blood (GSM18867
[NCBI GEO]
, GSM18868
[NCBI GEO]
), thymus (GSM18899
[NCBI GEO]
, GSM18900
[NCBI GEO]
), lymph node (GSM18903
[NCBI GEO]
, GSM18904
[NCBI GEO]
), lung (GSM18949
[NCBI GEO]
, GSM18950
[NCBI GEO]
), heart (GSM18951
[NCBI GEO]
, GSM18952
[NCBI GEO]
), liver (GSM18953
[NCBI GEO]
, GSM18954
[NCBI GEO]
), kidney (GSM18955
[NCBI GEO]
, GSM18956
[NCBI GEO]
), and skin (GSM19001
[NCBI GEO]
, GSM19002
[NCBI GEO]
) (available at http://www.ncbi.nlm.gov/geo; accession no. GSE1133
[NCBI GEO]
). Genes were selected on the basis of the GEArray S series human autoimmune and inflammatory responsegenearray(http://www.superarray.com/gene_array_product/HTML/HS-602.3.html). Analysis of the results was performed using the Spotfire program (Spotfire, Somerville, MA, http://www.spotfire.com). In addition, we used the following databases: Unigene, Entrez, LocusLink, and Geo from NCBI.
The 210865_at (U133A DNA microarray) probe was used to measure FasL mRNA expression in the aforementioned tissues.
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RESULTS |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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Transplantation and Differentiation of hESCs in the Trimera Model
The in vivo intensity by which the human immune system may act to reject hESC-derived transplants was evaluated using the human PBMC-reconstituted Trimera mouse model [27, 34] (supplementary online Fig. 1). Target cells or tissues were transplanted under the kidney capsule of the animals either before intraperitoneal PBMC reconstitution or 1 week after immunization by the same type of cells to PBMC-reconstituted animals. Such immunization generated a more robust allospecific response [27]. Grafts were harvested 3 to 5 weeks after transplantation, and human Ig-specific ELISA tests were used to confirm human PBMC engraftment [35]. Three weeks after transplantation of human adult skin grafts under the kidney capsule of nonimmunized PBMC-reconstituted mice, tissue damage and massive infiltration by CD45+ human leukocytes in the graft were observed in all cases (nine out of nine) (Fig. 1A). In contrast, approximately 1 x 106 undifferentiated hESCs transplanted under the kidney capsule of PBMC-reconstituted mice developed into teratoma tumors (10 to 20 mm), exhibiting normal growth rate (compared with nonreconstituted mice) and no tissue damage or infiltration by CD45+ leukocytes (10 out of 10) (Fig. 1B). Similarly, small-differentiated tissue fragments derived from a 4-week-old hESC-induced teratoma developed into teratoma structures after transplantation and PBMC reconstitution. Although these fragments are composed of multiple cell types, in these tumors only minor scattered infiltration was noted, with no apparent slowed growth rate or graft destruction (nine out of nine) (Fig. 1C). To confirm these results, we stained the same grafts by anti-human CD3 antibody. The staining could demonstrate that most of the infiltrating leukocytes in the graft are human T cells (supplementary online Fig. 2).
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). These data indicate that hESCs and their differentiated derivatives have little potential to activate a direct allospecific response by HLA nonmatched human lymphocytes.
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). We could confirm these results using the mouse anti-human FasL monoclonal antibody NOK-1 [36] (Fig. 2B). Therefore, we conclude that the resistance of hESCs to alloreactive T cells is not due to FasL expression, yet other mechanisms that might trigger activation-induced T cell death cannot be ruled out.
Multiple Factors Are Associated with the Reduced Immunogenicity of hESCs
The weak immune response toward hESCs also might be explained by T cell ignorance or anergy [37]. The two most important signals that must be delivered to T cells to induce their activation are engagement of the foreign MHC molecules with the T cell receptor and costimulation delivered mainly by costimulatory molecules, such as CD80 and CD86 molecules [38]. As demonstrated in our previous study, hESCs do not express MHC-II molecules, even after in vivo differentiation, but show low levels of MHC-I molecules, which are slightly induced by differentiation [23]. To test whether hESCs can also deliver costimulatory signals to T cells, we examined the expression of CD80 and CD86 on their cell surface by FACS (Fig. 2C). We found that the two proteins were not expressed on undifferentiated hESCs in contrast to control cells (B cell line). Moreover, application of IFN-, a known inducer of costimulatory molecules [38], did not induce CD80 and CD86 expression, although its receptor is expressed on the cells (not shown). Furthermore, a differentiated primary cell line derived from an hESC-induced teratoma (Tu cell line) was also found to be CD80 and CD86 negative, indicating that hESCs have a poor costimulatory capacity even after their differentiation and IFN- treatment.
To extend this analysis further, the transcription pattern of 306 genes that are known to be involved in immune responses was examined in hESCs and their differentiated progeny using 445 DNA microarray probe sets. This analysis included genes that encode for cytokines, chemokines and their receptors, leukocyte adhesion molecules, cell-surface receptors, signal transduction proteins, and transcription factors that mediate immune responses. Expression profiles were prepared from three independent samples of undifferentiated hESCs, 2-day-old EBs, 10-day-old EBs, 30-day-old EBs, and two 4-week-old teratomas [39] and compared with the expression profile of nine different leukocyte subsets and seven organs. Hierarchical clustering of the gene expression profiles shows that hESCs and their derivatives were clustered together in one group, which was separated from the other tissues (Fig. 3A). The most prominent distinction between the gene expression patterns of hESCs and the organs involves approximately 34 genes, which are highly expressed in the latter but were almost undetectable in hESCs and their derivatives (Fig. 3B). This gene expression signature includes diverse genes that are known to be especially important for T cell activation, such as the intercellular adhesion molecules-2 and -3 [40], interleukin-1ß [41], and CCL3 (MIP-1
) [42]. This pattern of gene expression clearly favors the ignorance hypothesis: hESCs and their differentiated derivatives only rarely differentiate to cells of the immune system that harbor the potential to properly stimulate immune responsiveness of alloreactive T cells. This notion is also supported by the fact that the genes that were upregulated in hESCs compared with the other samples do not possess known immune suppressive capacities (data not shown).
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). It is also crucial to test T cell response toward IFN-stimulated hESCs because these cytokines are released naturally during the course of many immune responses. Stimulatory leukocytes were produced by exogenously loading the HLA-A2-specific influenza virus type A (IV/A) matrix synthetic peptide GILGFVFTL on irradiated PBMCs from an HLA-A2+ donor. Coculture of these cells with untreated PBMCs from the same donor led to sensitization and expansion of HLA-A2-restricted and influenza peptide-specific CTLs.
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). In this test, synthetic IV/A peptide-loaded undifferentiated hESCs were not efficiently recognized by CTLs. Furthermore, even if undifferentiated hESCs were grown for 2 days in the presence of IFN- that induces MHC-I expression in these cells by 50-fold [23], killing efficiency was still very low. This is despite the fact that HLA-A2 levels on IFN--treated hESCs and 721.221/A2 are similar (Fig. 4A). Similarly, when naive and IFN--treated differentiated Tu cells were used as target cells in this assay, the cells were not killed by CTLs (Fig. 4B).
Next, we tested whether IV infection of hESCs and Tu-differentiated cell line enhances CTL-mediated cytolysis. Infection of target cells was confirmed by human anti-IV sera (data not shown). As expected, the control cell line HLA-A2/721.221 was killed effectively, whereas IV-infected undifferentiated hESCs were not killed (Fig. 4C). However, when the cells were infected and treated by IFN- simultaneously, effective killing response of at least 50% was noted (compared with the positive control). Surprisingly, this effect was less prominent when Tu cells were used. IV-infected IFN--treated Tu cells show clear but low lysis sensitivity (Fig. 4C). Taken together, these results demonstrate that hESCs might be recognized by human CTLs after strong stimulation of MHC-I expression. Also, killing efficiency by activated CTLs suggests that a very efficient peptide-loading method, such as a viral infection, is required to carry out cytotoxic assays against hESCs.
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DISCUSSION |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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Although it was recently reported that hESCs fail to elicit immune response in immunocompetent mice during the first 48 hours after intramuscular injection [44], we found that 1 month after transplantation, hESCs were totally eliminated in various strains of immunocompetent mice. In the experiments undertaken in mouse strains with different types of immune deficiency, T cell-deficient animals failed to reject hESC-derived graft, whereas the lack of NK cells or B cells did not interfere with vigorous hESC rejection. These findings clearly show the pivotal role of T cells in xenorejection of hESCs and their differentiated derivatives.
Using the humanized (Trimera) mouse model that enables evaluation of the direct immune rejection pathway [45], we investigated here for the first time allorejection of hESCs in vivo. Transplantation of hESCs and their differentiated derivatives to the human PBMC-reconstituted mice revealed that the cells uniformly escaped rejection and developed normally into teratomas. Similarly, hESC-derived primary cell lines and EBs were not rejected in this model, in contrast to human adult skin grafts or a B cell line, which were heavily infiltrated by leukocytes or completely eliminated. These results indicate that hESCs and their differentiated progeny have reduced immunogenicity (capacity to evoke immune response) compared with adult tissues and do not elicit direct allorejection. A special emphasis should be given to the fact that teratomas contain multiple terminally differentiated cell types, as in conventional grafts.
The resistance of hESCs to direct T cell-mediated allorejection may emanate from reduced potential to properly stimulate alloreactive T cells, from immune protective mechanisms, or from both. Clearly, hESCs and their derivatives fail to properly deliver the right stimulatory signals: they express only low levels of MHC-I molecules, MHC-II molecules are absent [23], and, as shown here, CD80 and CD86 proteins are not expressed. In contrast, control grafts that were used as a positive control contain MHC-II-expressing cells and are therefore likely to be rejected by initial activation of CD4+ T cells. Raji cells are MHC-II-expressing cells, and human skin grafts contain APCs that express MHC-II molecules, both of which can migrate into regional lymph nodes and stimulate alloresponse against the graft. These findings suggest that despite multilineage differentiation of hESCs, observed in teratomas, substantial development of MHC-II-expressing cells such as APCs does not occur in the grafts. This highlights the ability to transplant purified hESC-derived MHC-II-negative populations that have reduced capacity to activate immune response.
As shown recently, donor endothelial cells in human grafts can function as APCs and/or targets for T-cell-mediated cytotoxicity and trigger acute rejection [46]. Yet, in this study we did not see any significant sign for rejection of hESC-derived teratomas, although it was shown recently that hESC-derived endothelial structures formed in teratomas [47]. Hence, it is reasonable to assume that hESC-derived vasculature does not considerably contribute to activation of allogeneic immune responses. It remains to be determined whether more mature hESC-derived endothelial cells will acquire APC functions after prolonged differentiation.
Although FasL expression was suggested to be involved in protecting RESC-like populations from rejection by allogeneic hosts [26], this seems not to be the case for hESCs. As demonstrated in this study, FasL mRNA and its protein could not be detected in hESCs and EBs; thus, it seems that the protective capacity of FasL is species-specific and is absent in hESCs. It is more likely that the capacity to survive in an allogeneic environment is due to ignorance by T cells [37].
It was recently suggested that immunological maturity is a rather late event during the gestational period of human embryos [34]. Our DNA microarray data support this notion. The expression of approximately half of the immune-related genes that were expressed in hematopoietic cells, lymphoid organs, and other tissues was not upregulated during in vitro and in vivo differentiation of hESCs, indicating that using most of the currently available differentiation protocols, the cells do not reach immunological maturity. These data suggest that immunosuppressive regimes for hESC-based therapeutics could be highly reduced compared with conventional organ transplantation. Still, it is important to note that whether or not hematopoietic differentiation take place and T cell sensitization occurs, the MHC-I levels in hESCs are sufficient for T cell recognition, as shown by the CTL assays. Thus, any hematopoietic cells or progenitors should be eliminated before transplantation if they are therapeutically unnecessary. Also, it is possible that after transplantation the cells would further mature and start to express higher levels of transplantation antigens. To examine this possibility, the immunological properties of hESC-derived tissues should be evaluated in long-term studies.
Finally, because cross priming of human T cells by mouse APCs is weak in the Trimera model [34], it is likely that rejection of hESCs and their differentiated progeny in immunocompetent mice is mediated indirectly upon triggering of mouse T cells by mouse APC-presenting human antigens originating from the implant. Dekel et al. [34] have recently demonstrated that early embryonic pig kidney precursor tissues from E28 in contrast to E42 tissues evade rejection in the Trimera model by human lymphocytes. The same tissues are rejected in normal immunocompetent mice, but this rejection can be overcome by mild immunosuppression with costimulatory blockade agents such as CTLA4. The potential of such agents in overcoming rejection of hESCs and their differentiated derivatives should be further investigated in preclinical large-animal models.
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ACKNOWLEDGMENTS |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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DISCLOSURES
The authors indicate no potential conflicts of interest.
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REFERENCES |
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 S.-W. Cho, S.-H. Moon, S.-H. Lee, S.-W. Kang, J. Kim, J. M. Lim, H.-S. Kim, B.-S. Kim, and H. M. Chung Improvement of Postnatal Neovascularization by Human Embryonic Stem Cell-Derived Endothelial-Like Cell Transplantation in a Mouse Model of Hindlimb Ischemia Circulation, November 20, 2007; 116(21): 2409 - 2419. [Abstract] [Full Text] [PDF]
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 G. Condorelli and D. Catalucci Human Stem Cells for Heart Failure Treatment: Ready for Prime Time? J. Am. Coll. Cardiol., November 6, 2007; 50(19): 1894 - 1895. [Full Text] [PDF]
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B. Coleman, M. G. de Silva, and R. K. Shepherd Concise Review: The Potential of Stem Cells for Auditory Neuron Generation and Replacement Stem Cells, November 1, 2007; 25(11): 2685 - 2694. [Abstract] [Full Text] [PDF]
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G. Brunlid, J. Pruszak, B. Holmes, O. Isacson, and K.-C. Sonntag Immature and Neurally Differentiated Mouse Embryonic Stem Cells Do Not Express a Functional Fas/Fas Ligand System Stem Cells, October 1, 2007; 25(10): 2551 - 2558. [Abstract] [Full Text] [PDF]
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 P. Batten, N. A Rosenthal, and M. H Yacoub Immune response to stem cells and strategies to induce tolerance Phil Trans R Soc B, August 29, 2007; 362(1484): 1343 - 1356. [Abstract] [Full Text] [PDF]
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B. Blum and N. Benvenisty Clonal Analysis of Human Embryonic Stem Cell Differentiation into Teratomas Stem Cells, August 1, 2007; 25(8): 1924 - 1930. [Abstract] [Full Text] [PDF]
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S. Levenberg, J. Zoldan, Y. Basevitch, and R. Langer Endothelial potential of human embryonic stem cells Blood, August 1, 2007; 110(3): 806 - 814. [Abstract] [Full Text] [PDF]
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F. Nakajima, K. Tokunaga, and N. Nakatsuji Human Leukocyte Antigen Matching Estimations in a Hypothetical Bank of Human Embryonic Stem Cell Lines in the Japanese Population for Use in Cell Transplantation Therapy Stem Cells, April 1, 2007; 25(4): 983 - 985. [Abstract] [Full Text] [PDF]
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 Z. Abdullah, T. Saric, H. Kashkar, N. Baschuk, B. Yazdanpanah, B. K. Fleischmann, J. Hescheler, M. Kronke, and O. Utermohlen Serpin-6 Expression Protects Embryonic Stem Cells from Lysis by Antigen-Specific CTL J. Immunol., March 15, 2007; 178(6): 3390 - 3399. [Abstract] [Full Text] [PDF]
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C.-J. Chang, M.-L. Yen, Y.-C. Chen, C.-C. Chien, H.-I. Huang, C.-H. Bai, and B. L. Yen Placenta-Derived Multipotent Cells Exhibit Immunosuppressive Properties That Are Enhanced in the Presence of Interferon-{gamma} Stem Cells, November 1, 2006; 24(11): 2466 - 2477. [Abstract] [Full Text] [PDF]
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C. Ellerstrom, R. Strehl, K. Moya, K. Andersson, C. Bergh, K. Lundin, J. Hyllner, and H. Semb Derivation of a Xeno-Free Human Embryonic Stem Cell Line Stem Cells, October 1, 2006; 24(10): 2170 - 2176. [Abstract] [Full Text] [PDF]
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S. Bonde and N. Zavazava Immunogenicity and Engraftment of Mouse Embryonic Stem Cells in Allogeneic Recipients Stem Cells, October 1, 2006; 24(10): 2192 - 2201. [Abstract] [Full Text] [PDF]
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M. S. Rao One Successful Series Begets Another Stem Cells, October 1, 2006; 24(10): 2160 - 2161. [Full Text] [PDF]
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 O. Caspi and L. Gepstein Stem cells for myocardial repair Eur. Heart J. Suppl., September 1, 2006; 8(suppl_E): E43 - E54. [Abstract] [Full Text] [PDF]
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