人骨髓间充质干细胞体外对异基因T淋巴细胞表型的影响

为了研究间充质干细胞 (mesenchymalstemcell,MSC)的免疫调节作用 ,探讨防治异基因骨髓移植中移植物抗宿主病 (GVHD)和移植排斥反应 (HVGR)的可能途径 ,从人骨髓中分离培养间充质干细胞 ,并通过其形态的均一性及流式细胞术检测表面标志以鉴定其纯度 ,将MSC分别以 8× 10 4 (A组 )、4× 10 4 (B组 )和 2× 10 4 (C组 )个细胞 孔分别接种于 6孔板 ,并与经分离的外周血T淋巴细胞共培养 7天 ,以单独培养的外周血T淋巴细胞为对照组 ,用流式细胞仪分别在培养 0、2 4、72小时和 7天测定各组T细胞上CD3、CD4、CD8、CD2 5表达的变化。结果表明 :T细胞和MSC共培养组与T细胞单独培养组相比 ,A组和B组CD4 CD2 5 免疫调节性T细胞和CD8 T细胞明显增多 ,A组和B组之间无明显差别。实验组和对照组相比CD3、CD4、CD2 5表达无明显差别。结论 :骨髓MSCs在体外可使外周血T细胞表型发生改变 ,CD4 CD2 5 免疫调节性T细胞和CD8 T细胞明显增多 ,本研究结果为临床异基因造血干细胞移植预防GVHD时MSCs的输注数量提供了参考。     

T cell transduction and suicide with an enhanced mutant thymidine kinase

Retroviral transfer of Herpes simplex virus thymidine kinase to T cells has been used to confer sensitivity to the antiviral agent ganciclovir. This has allowed therapeutic approaches to be developed in which T cells mediating graft-versus-host disease after bone marrow transplantation can be selectively eliminated by the administration of ganciclovir. Although the strategy has been shown to be generally successful in early clinical trials, there are concerns about possible resistance to ganciclovir and the risk of myelosuppressive side-effects at the doses required to induce T cell suicide. We have incorporated the enhanced mutant HSV-TKSR39 into retroviral vectors tailored to exhibit high levels of expression in T cells and have used protocols optimized for the transduction and selection of primary lymphocytes. We demonstrate that leukemic and primary T cells can be efficiently transduced and highly enriched under conditions that should be readily adaptable for clinical use. T cells carrying HSV-TKSR39 were inhibited by exposure to ganciclovir at concentrations an order of magnitude below those required for wild-type HSV-TK. The less toxic agent aciclovir also eliminated T cells transduced with HSV-TKSR39 (but not HSV-TK), underlining the increased therapeutic potential of the mutant suicide gene system in the bone marrow transplantation setting.     

Monitoring of developing graft-versus-host disease mediated by herpes simplex virus thymidine kinase gene-transduced T cells

Introduction of the HSV-Tk suicide gene into allogeneic T cells offers the possibility to control developing host-reactive cells within the context of allogeneic bone marrow transplantation (BMT). Sensitive quantitative detection methods are a prerequisite to monitor genetically modified T cells in peripheral blood and tissues to study their involvement in graft-versus-host disease (GVHD)-induced lesions as well as their disappearance or persistence after ganciclovir (GCV)-induced suicide. We monitored the alloreactivity of HSV-Tk-transduced T cells after BMT by studying their in vivo distribution and quantity in peripheral blood and in tissues in a WAG/Rij into Brown Norway fully mismatched rat allogeneic BMT model. Genetically modified T cells were quantified in blood and tissues by fluorescence-activated cell sorting, immunohistochemical analysis, and real-time quantitative polymerase chain reaction (PCR) analysis. A significant increase in the number of allogeneic HSV-Tk(+) T cells was found in particular in spleen and lymph nodes and large numbers were found in tongue, skin, and intestines. In blood, an increase in HSV-Tk(+) T cells closely preceded clinical symptoms of GVHD. Real-time quantitative PCR proved to be a fast and accurate tool by which to quantify transduced T cells both in blood and tissues. This enables the study of the in vivo alloreactivity of retrovirus-transduced cells and the response of HSV-Tk-expressing T cells to GCV-induced suicide therapy. Furthermore, we showed the potential use to study specific cause-effect relationships in a broad range of animal and clinical studies involving genetically engineered cells.     

Influence of ex vivo expansion and retrovirus-mediated gene transfer on primary T lymphocyte phenotype and functions

To modulate alloreactivity after hematopoietic stem cell (HSC) transplantation, suicide gene-expressing donor T cells can be administered with an allogeneic T cell-depleted HSC graft. Immune competence of such cells is a critical issue. We have examined the impact of our ex vivo gene transfer protocol (12-day culture period including CD3/IL-2 activation, retrovirus-mediated gene transfer, and G418-based selection) on the phenotype and functional properties of gene-modified cells (GMC). GMC were compared with control cells that had been cultured in parallel with GMC, but nontransduced and nonselected, as well as with peripheral blood mononuclear cells (PBMC). Our data show that phenotypical modifications are similar in control cells and GMC, demonstrating that alterations result from the 12-day culture rather than from the transduction and/or selection process itself. Such modifications include a reversal of CD4/CD8 ratio, activated phenotype (increased expression of CD45RO, CD95, and HLA-DR), and acquisition or increased expression of co-stimulatory molecules (CD80, CD86, and CD40). This led to an enhanced allostimulating potential of GMC, as compared with resting T cells, when used as stimulating cells in mixed lymphocyte reactions. Conversely, when using them as responder cells in mixed lymphocyte reactions, GMC exhibited a rapid loss of alloreactivity that resulted both from culture-dependent and from transduction and/or selection-dependent events. In conclusion, the retrovirus-mediated gene transfer can be associated with major phenotypical and functional alterations that could have strong clinical implications (increased immunogenicity, reduced anti-leukemic effect). Thus, future T cell expansion protocols should try to improve not only cell expansion or gene transfer efficiency, but also T cell functions.     

Correlation of time to platelet engraftment with amount of transplanted CD34+CD41+ cells after allogeneic bone marrow transplantation

A major problem after autologous or allogeneic stem cell transplantation is prolonged thrombocytopenia. There are several studies published about correlations of the composition of the graft and time to platelet engraftment for autologous transplantation but only a few studies for allogeneic transplantation. In our study, we wanted to find out whether the correlation between the time to platelet engraftment and amount of transplanted CD34(+)CD41(+) cells described previously after autologous peripheral blood stem cell transplantation could be reproduced in the allogeneic bone marrow transplantation setting. We found correlations not only for the number of transplanted CD34(+) cells with the time to leukocyte engraftment (r = -0.32, p = 0.045) but also for the number of transplanted CD34(+)CD41(+) cells and time to platelet engraftment (r = -0.34, p = 0.038), which were both statistically significant. A significant correlation between transplanted CD34(+) cells versus platelet engraftment and transplanted CD34(+)CD41(+) cells versus leukocyte engraftment was not found. The finding that the amount of committed megakaryocyte progenitor cells in the graft is an important predictive factor for platelet engraftment after allogeneic bone marrow transplantation might be the base for future studies of ex vivo expansion of clonable megakaryocyte precursors.     

Blood versus marrow hematopoietic allogeneic graft.

Allogeneic G-CSF-mobilized blood cell transplantation (BCT), an alternative to allogeneic bone marrow transplantation (BMT), is associated with enhanced engraftment and accelerated hematopoietic recovery. In addition, immune reconstitution and overall alloreactivity after BCT versus BMT differ significantly. Indeed, despite an increased number of donor T cells infused, the incidence of acute graft-versus-host disease (GvHD) after BCT appears to remain identical or lesser than after BMT. On the other hand, a higher risk of chronic GvHD has been reported after BCT. In a SFGM phase III trial, 101 patients with early leukemia and an HLA-matched sibling donor randomly received a BCT or BMT. BCT was associated with a higher number of infused CD34+ cells, accelerated platelet and neutrophil reconstitution, fewer platelet transfusions and similar acute GvHD incidence. However, chronic GvHD occurred more frequently after BCT. With a median follow-up of 20 months, relapse, survival and leukemia-free survival were not different. In the course of this study, immune parameters related to the graft as well as to early reconstitution were prospectively examined. T cells subsets, B cells, NK cells and monocytes numbers were significantly higher in BC grafts (versus BM). T cells in BC grafts were less activated than in BM grafts. Frequency of IFN-gamma, IL-2- and TNF-alpha-secreting cells and single-cell IFN-gamma production potential was reduced in BC graft. One month after BCT, blood T-cell counts were 3-fold higher than after BMT. Moreover, post-BCT T cells were less activated and counts correlated with the number of T cells infused with the graft, which was not the case after BMT. Several acute hemolysis episodes, resulting from anti-A and/or -B donor-derived Ab directed at Ag present on recipient red blood cells (minor ABO mismatch), have been described after BCT. Recipients indeed exhibited significantly increased anti-A and/or -B Ab titers after BCT, particularly in the setting of a "minor" ABO mismatch. Furthermore, the frequency of anti-HLA Ab early after BCT was significantly increased (despite the reduction in platelet transfusion requirements). The higher number of activated B cells and/or CD4 T cells and monocytes in a BCT graft and/or the higher number of circulating CD4 T- and B-cells after BCT could be associated with the enhanced alloAb production. G-CSF-induced TH2 cytokine profile of the T cells present in the graft could also be contributive. Recent studies have determined that BC grafts contained a higher number of type 2 dendritic cells (DC2), themselves associated with high frequencies of TH2 CD4+ cells. Since chronic GvHD is associated with the occurrence of Ab-mediated auto-immune-like syndromes, it is tempting to speculate that a higher incidence of chronic GvHD may result from these findings. In conclusion, BCT results in clinically relevant distinct hematopoietic and immune reconstitution patterns.     

Efficient bone marrow transduction by gene transfer with allogeneic umbilical cord blood serum and plasma: an implication for clinical trials

Low in vivo transduction efficiency and safety concerns have been hurdles for effective hematopoietic stem cell (HSC) gene therapy. Here, we investigate whether the safety and efficiency of retroviral gene transfer into HSCs can be improved by using human allogeneic umbilical cord blood (UCB)-derived supplements instead of fetal bovine serum (FBS). When CD34(+) cells were cultured ex vivo in UCB-derived serum (CBS) or plasma (CBP), comparable or higher maintenance of HSCs was observed than in FBS and serum-free substitution medium (SFM) as assessed by the frequency of positive engraftment and the level of engraftment in NOD/SCID mice after transplantation of cultured cells. CBS and CBP also exhibited higher level stabilization of retroviral particles than SFM during in vitro culture of retrovirus pseudotyped with gibbon ape leukemia virus or vesicular stomatitis virus glycoprotein. Retroviral gene transfer into CD34(+) cells performed with CBS or CBP resulted in increased gene transfer into CD34(+) cells and increased transduction of reconstituted bone marrow cells compared to transfers with SFM or FBS. The increased transduction of bone marrow cells was associated with a larger number of transduced progenitors in the recipient mice. Significant oligoclonality in the transduced progenitors, as determined by ligation-mediated polymerase chain reaction, suggested efficient retroviral targeting of multiple HSCs in the CBS- or CBP-supplemented media. Combined, our results show that allogeneic UCB-derived serum or plasma is a safe and easily accessible serum supplement that can support efficient retroviral gene transfer into HSCs for the clinical-grade manipulation of HSCs.     

Preparation of genetically homogeneous antigen-specific thymidine kinase positive T-lymphocyte clones for the control of alloreactivity post-bone marrow transplantation

We have previously proposed the use of HLA-specific T-cell clones transduced with a suicide gene to produce an allogeneic effect that can be controlled after allogeneic bone marrow transplantation. Procedures described so far to obtain specific T-cells transduced with a suicide gene have led to the recovery of heterogeneous polyclonal T-cells with a limited level of purity. We have therefore developed an approach to select specific T-cell clones in which the suicide transgene is inserted at a unique site of the genome, and used it to produce CD(+)-cytotoxic HLA-DP-specific T-cell clones. Immunization was performed by a one-way mixed lymphocyte culture and responder T lymphocytes were transduced at day 16, 6 days after the second stimulation. Transductions were carried out using gibbon ape leukemia virus (GALV)-pseudotyped retroviral particles harboring a bicistronic Thy-1/TK vector produced by TEFLY GA16-pKM4 clone 34 packaging cells. Three to 5 days later, CD90 immunomagnetic selection and cloning were performed on the transduced T cells. Our results demonstrate that this procedure led to the recovery of T-cell clones, the majority of which had the expected specificity and a single site of transgene insertion. Such clonotransgenic T-cell populations represent suitable tools to drive a defined alloreaction that can be controlled after bone marrow transplantation.     

复制缺陷性慢病毒介导的双自杀基因在小鼠异基因骨髓移植中的应用

目的　探讨复制缺陷性慢病毒介导的胞嘧啶脱氨酶 (cytosinedeaminase,CD)和胸苷激酶(thymidinekinase ,TK)双自杀基因在异基因骨髓移植 (allo BMT)时控制移植物抗宿主病 (GVHD)的可行性及其有效性。方法　将携带双自杀基因的复制缺陷性慢病毒通过脂质体转染入T细胞中。将经6 0　Coγ射线照射后的荷瘤小鼠分组进行骨髓移植 ,观察骨髓移植后荷瘤鼠CFU S、CFU GM、Y染色体整合、T细胞中CD TK基因整合、生存率和生存期、体重及病理组织学等指标。结果　复制缺陷性慢病毒载体可将双自杀基因高效稳定转染入T细胞。在allo BMT中 ,除空白对照组外 ,各组小鼠的CFU S的数目和CFU GM产率差异无显著性 ,且均有Y染色体整合。使用前体药物治疗的小鼠未发生明显的GVHD ,其生存率和生存期明显高于其它各组 ;双自杀基因的效果优于单自杀基因。结论　复制缺陷性慢病毒介导的双自杀基因系统可在不影响移植物存活的情况下有效控制GVHD的发生 ,显著提高allo BMT的成功率。     

Suppression of graft-versus-host disease and amplification of graft-versus-tumor effects by activated natural killer cells after allogeneic bone marrow transplantation.

Bone marrow transplantation (BMT) is currently used for the treatment of a variety of neoplastic diseases. However, significant obstacles limiting the efficacy of allogeneic BMT are the occurrence of graft-versus-host disease (GvHD) and tumor relapse. Natural killer (NK) cells exert a variety of immunologic and homoeostatic functions. We examined whether adoptive transfer of activated NK cells of donor type would prevent GvHD after allogeneic BMT in mice. Lethally irradiated C57BL/6 (H-2(b)) mice, were transplanted with MHC incompatible BALB/c (H-2(d)) bone marrow cells and spleen cells and rapidly succumbed to acute GvHD. In contrast, mice that also received activated NK cells of donor type exhibited significant increases in survival. In determining the mechanism by which the NK cells prevented GvHD, mice were concurrently treated with a neutralizing antibodies to the immunosuppressive cytokine TGFbeta. Anti-TGFbeta completely abrogated the protective effects of the activated donor NK cells indicating that TGFbeta plays an important role in the prevention of GvHD by NK cells. We then examined whether activated NK cells of donor type after allogeneic BMT would induce graft-versus-tumor (GvT) effects without GvHD in mice bearing a murine colon adenocarcinoma (MCA-38). 10 d after receiving the tumor, in which the mice had demonstrable lung metastases, recipients received an allogeneic BMT with or without activated NK cells. Administration of activated NK cells resulted in significant GvT effects after allogeneic BMT as evidenced by increases in median survival and fewer lung metastasis. No evidence of GVHD was detected compared with recipients receiving spleen cells alone which also developed fewer lung metastases but in which all had succumbed to GVHD. Thus, our findings suggest that adoptive immunotherapy using activated donor NK cells combined with allogeneic BMT inhibits GvHD and promotes GvT in advanced tumor-bearing mice. These results also suggest that GvT and GvHD can be dissociable phenomena.     

Graft T-cell depletion as a prerequisite for the modulation of alloreactivity after haematopoietic stem cell transplantation

The T-lymphocytes present in the graft, HLA compatibility, and the cytokine environment at the time of transplantation play a major role in alloreactivity. Increased knowledge of the on-going immunological interactions as well as the development of cellular therapy are required to permit further expansion of post-transplantation alloreactivity as an important immunotherapy tool. By allowing successful GvHD prevention and various post-transplantation immunological interventions, T-cell depletion of the graft can be the starting point for a multistage "progressive" procedure transplantation process adapted to recipient disease, HLA compatibility, desired anti-tumour effects and observed alloreactivity.     

Minor histocompatibility antigen-specific cytotoxic T cell lines, capable of lysing human hematopoietic progenitor cells, can be generated in vitro by stimulation with HLA-identical bone marrow cells

Recipient-antidonor alloreactivity before HLA genotypically identical bone marrow transplantation (BMT) between donor-recipient pairs that are negative in the mixed lymphocyte reaction (MLR), the cell-mediated lympholysis (CML) assay, and the lymphocyte crossmatch was not detectable in the majority of cases, using recipient peripheral blood lymphocytes (PBL) collected before BMT as responder cells and donor PBL as stimulator cells. However, when donor bone marrow mononuclear cells (BMMNC) instead of PBL were used as stimulator cells, we could detect donor-specific alloreactivity in 7 of 10 HLA genotypically identical donor-recipient pairs. To demonstrate that this alloreactivity was minor histocompatibility (mH) antigen specific and not directed against HLA class I splits or variants, two cytotoxic T lymphocyte (CTL) lines were tested in further detail against phytohemagglutinin (PHA) blasts from pairs of HLA genotypically identical siblings positive for the HLA class I restriction molecule. Both CTL lines recognized mH antigens, as illustrated by the differential recognition of PHA blasts of one of the two siblings from several pairs. The potential role of these mH antigen-specific CTLs in bone marrow graft rejection was demonstrated by the mH antigen-specific growth inhibition of hematopoietic progenitor cells from the original bone marrow donor and from HLA class I restriction molecule-positive individuals who expressed the mH antigens on their PBL and BMMNC. Our assay can be used in HLA genotypically identical BMT to detect a recipient-antidonor response, directed against cellularly defined mH antigens expressed on donor HPC, BMMNC, and PBL, before transplantation.     

Early immune response against retrovirally transduced herpes simplex virus thymidine kinase-expressing gene-modified T cells coinfused with a T cell-depleted marrow graft: an altered immune response?

Administration of herpes simplex thymidine kinase (HSV-tk)-expressing, gene-modified T cells (GMCs) with T cell-depleted bone marrow transplantation (TCD-BMT) can allow modulation of posttransplantation alloreactivity. Twelve patients received 2 x 10(5) to 2 x 10(6) CD3+ donor GMCs per kilogram with HLA-identical sibling TCD-BMT. Despite extensive T cell depletion of bone marrow, an intensive conditioning regimen, and immunosuppressive graft-versus-host disease (GvHD) prophylaxis, infusion at the time of TCD-BMT of this low number of GMCs sufficed to induce a rapid GMC-specific immune response, as detected by interferon- enzyme- linked immunospot assay in six of eight patients, preferentially targeting HSV-tk. Maximal responses were reached early (median time, 49 [35-68] days post-BMT), with a subsequent rapid and significant decrease in five of six evaluable patients. Immune responses were negatively correlated with the maximal circulating GMC counts. However, such immune response did not result in the elimination of circulating GMCs and was not associated with measurable ex vivo cytotoxic activity against GMCs. Furthermore, alloreactive GMCs still could induce GCV-sensitive GvHD in one patient despite an ongoing immune response. Overall, infusion of HSV-tk-expressing GMCs at the time of BMT results in an early immune response. Such immune response may be altered and may not prevent persistent GCV-sensitive alloreactivity.     

Development of a competitive PCR method for in vitro and in vivo quantification of herpes simplex virus thymidine kinase and neomycin resistance-expressing cells used in a clinical trial

The aim of this study was to set up a sensitive and specific method to quantify the number of gene-modified cells in a gene therapy clinical trial currently underway at our institution. This trial involves the use of retrovirally transduced allogeneic T cells expressing the herpes simplex-1 thymidine kinase (HSV-TK) and neomycin-phosphotransferase (NeoR) resistance gene. Quantification by competitive PCR was performed, with two homologous internal standards (deltaTK, deltaNeoR), 30 bp shorter than the target sequences (TK, NeoR), coupled to fluorescent laser-based detection. Assessment of the amplification systems procedures was carried out for each sequence. The 30-bp deletion did not affect the amplification efficiency significantly. Determination of the plateau phase of both amplified sequences demonstrated that each sample must be quantified during the predetermined exponential phase. Finally, a blinded study of a transduced cell dilutions panel validated the overall methodology. The competitive PCR was applied to quantification of the retroviral transduction process by quantifying the NeoR gene in transduced PBMC samples (prior to G418 selection) from 18 donors in our clinical trial. A mean transduction efficiency of 9.78% +/- 1.37% was observed. We also quantified TK-expressing donor transgenic T cells in a murine GvHD model. Results demonstrated on initial expansion of donor HSV-TK- expression T cells as well as a significant ganciclovir (GCV)-induced decrease correlated with the number of circulating gene-modified T cells. Therefore, we have developed an efficient gene quantification tool that should be useful for in vivo monitoring of gene-modified cells.     

骨髓间充质干细胞抑制异体T淋巴细胞反应的实验研究

目的了解骨髓间充质干细胞(MSC)能否诱导异体T淋巴细胞反应性下降,探讨防治异基因造血干细胞移植中移植物抗宿主病的途径。方法骨髓来源的MSC经60Co照射后与异体T淋巴细胞共培养,用3H-TdR掺入的方法测定共培养前后T淋巴细胞增殖状态及对异体细胞和非特异性分裂原刀豆素A(ConA)的反应性变化。结果MSC与异体T淋巴细胞共培养后,并不刺激T淋巴细胞的增殖;MSC作为刺激细胞与异体T淋巴细胞的首次及二次接触均不引起T淋巴细胞活化。单独T淋巴细胞的放射性核素每分钟闪烁计数(CPM)值为27529±969,首次接触与二次接触的CPM值分别为9126±654及13260±874。混合淋巴细胞反应结果表明,与MSC共孵育后的异体T淋巴细胞对MSC同源淋巴细胞反应性下降,共孵育前的CPM值为45876±5285,共孵育后的CPM值为9850±1618,ConA刺激的细胞增殖活性也显著减低。结论骨髓MSC在体外可使异体T淋巴细胞对异体抗原的反应性减低,这种作用与其低免疫原性有关。     

Two-stage separation of immature and mature T lymphocytes from myeloerythroid clonogenic bone marrow cells by apheresis and elutriation centrifugation

Because graft-versus-host disease remains a major complication in allogeneic bone marrow transplantation, a number of techniques capable of removing mature T lymphocytes from bone marrow cells have been attempted. The authors describe a simple two-step procedure using counterflow centrifugation elutriation (CCE) that eliminated 95 to 98 percent of the mature T lymphocytes and greater than 97 percent of the T lymphocyte colony-forming units (CFU-T) while concentrating the bone marrow myeloid colony-forming cells. Viability was greater than 98 percent, and 72 to 98 percent of the total cells separated were recovered. Lymphocyte depletion was substantiated by both morphologic and phenotypic criteria using monoclonal antibodies to T lymphocytes, as well as by responsiveness in mixed-lymphocyte cultures and to mitogens. In addition, this technique separated the lymphoid colony-forming cells from the larger myeloid colony-forming cells. It was concluded that this simple two-step CCE procedure can be used to separate T lymphocytes and CFU-T from myeloid colony-forming cells and offers a means of purging T lymphocytes from large numbers of marrow cells that may be required for human allogeneic bone marrow transplantation.     

混合骨髓移植的实验研究

目的：探讨在异基因骨髓移植治疗白血病中既控制移植物抗宿主病（ＧＶＨＤ）又同时保留移植物抗白血病（ＧＶＬ）作用的移植方案。方法：采用近交系小鼠移植模型，在异基因骨髓、脾细胞移植物中混合一定比例的同基因脾细胞，观察移植后受鼠ＧＶＨＤ死亡率、脾结节数、移植后不同时间骨髓造血重建细胞来源以及受鼠脾脏淋巴细胞对供、受鼠双方来源的刺激细胞增殖反应；采用Ｌ６１５小鼠白血病模型观察混合移植对荷瘤小鼠生存时间及死亡原因的影响。结果：混合移植可以有效减轻ＧＶＨＤ，异基因造血免疫细胞在受鼠体内一过性存留并发挥移植物抗宿主反应，使荷瘤小鼠生存时间明显延长。结论：异基因骨髓、脾细胞移植物中混合一定比例的同基因脾细胞使移植受鼠体内既具有主要组织相容性抗原复合物（ＭＨＣ）不合的免疫活性细胞发挥一过性ＧＶＬ作用，同时减轻了异基因骨髓移植的严重ＧＶＨＤ。     

混合骨髓移植——协调GVHD与GVL的移植新策略

移植物抗宿主病(GVHD)与移植物抗白血病(GVL)本质上都是异基因淋巴细胞针对受者MHC的以细胞免疫反应为主的排斥反应。由于存在不依赖GVHD的GVL,以及正常组织对损伤的代偿修复能力,如果把GVHD控制在一定程度之内,就可以保留GVL作用。在异基因移植物中加入同基因成分进行混合移植,为协调GVHD与GVL提示了一种新的移植策略。异基因淋巴细胞是GVL所必需的效应细胞,同基因淋巴细胞可以通过对后者的抑制减轻GVHD的同时保留GVL。GVHD与GVL的平衡可以通过改变同基因与异基因淋巴细胞的比例而实现。临床混合骨髓移植已取得初步成效。     

免疫磁珠选择性清除人异基因反应性T细胞的实验研究

本研究用磁性细胞分离系统清除CD25^＋和CD69^＋人同种异体反应性T细胞，为减轻异基因骨髓移植后的移植物抗宿主病探索新的手段、对健康供者外周血单个核细胞与白血病缓解病人的骨髓单个核细胞进行单向混合淋巴细胞培养。3天后，通过磁性细胞分离系统清除CD25^＋和CD69^＋的同种异体反应性T细胞；通过^3H-TdR掺入实验，观察处理后的供者外周血单个核细胞对同一病人的骨髓单个核细胞及无关者外周血单个核细胞的反应性．结果表明：与未清除组相比，清除后供者细胞对同一病人抗原的反应性降低50％，但保留了大部分对无关者抗原的反应性。结论：在体外反应中清除同种异体反应性T细胞可降低对刺激抗原反应，同时保留大部分对无关者抗原的反应。     

T regulatory cell separation for clinical application

We selected T regulatory cells (Tregs) from standard leukapheresis using double-negative selection (anti-CD8 and anti-CD19) followed by positive selection (anti-CD25) and 72 procedures were performed. A median of 263×10(6)cells (range 143-470×10(6)) were recovered with a mean of CD4(+)/CD25(+) cells of 94.5±2.4% (36.5±18.6% CD4(+)/CD25(+hi)). FoxP3(+) cells were equal to 79.8%±22.2. CD127(+) cells were 12.5%±8.2. The inhibition assay showed an inhibition rate of 67±22. Cells isolated by means of this approach can be used in allogeneic hematopoietic stem cell transplantation to reduce the incidence and severity of GvHD without bystander inhibition of general immunity.