CD4^＋CD25^＋Foxp3^＋调节性T细胞的体外扩增及其在移植物抗宿主病中的应用

同种异基因造血干细胞移植是急、慢性白血病及其他恶性血液病重要的治疗方法,但急慢性移植物抗宿主病（graft—versus-host disease,GVHD）作为异基因造血干细胞移植的主要并发症严重影响移植患者的存活率,阻碍移植的临床推广。很多研究发现,高表达Foxp3的CD4^＋CD25^＋调节性T细胞（regulatory T cells,Treg）不仅能控制急慢性GVHD的发生,而且不影响移植物抗白血病效应（graft-versusleukemia,GVL）,在急慢性GVHD发生发展及治疗方面有重要的作用。但Treg细胞在体内的数量很少,不能满足临床应用需求。目前应用外源的IL-2联合TCR、CD28信号通路共同刺激以及运用树突状细胞（dendritic cell,DC）刺激均能达到体外有效扩增Treg细胞的目的。这些扩增的Treg细胞在控制造血干细胞移植过程中急慢性GVHD的发生及防治自身免疫性疾病和移植排斥等方面具有明显作用,在疾病控制和临床应用中具有广阔前景。     

未成熟树突状细胞防治移植物抗宿主病的实验研究

目的：观察供者未成熟树突状细胞（imDC）刺激自体T细胞增殖的能力,探讨利用imDC防治移植物抗宿主病（GVHD）临床应用的可行性。方法：Ak健康供者外周血分离单核细胞,采用重组人粒细胞巨噬细胞集落刺激因子（rhGM-CSF）和白细胞介素（IL）4联合培养4d,诱导其分化成imDC;培养7d,分化成mDC。并通过倒置显微镜和HE染色观察细胞形态、流式细胞仪检测细胞表型。采用MLR方法,构建GVHD发生机制的模型,比较供者imDC和mDC刺激自体T细胞增殖的能力。结果：（1）培养4天后细胞具有典型的imDC特征,CDla、CD83和双抗分别表达为55．79％、64、67％和46、67％,成熟标志CD83表达较低;培养7天后具有典型mDC特征,CDla、CD83和双抗表达分别为61．56％、82．40％和64．12％,成熟标志CD83表达较高。（2）MLR法共孵育72小时后,加入CCK-8检测OD值,imDC组与对照组比较无统计学意义（P〉0．05）,不能刺激自体T细胞增殖（SI〈1．00）;mDC组与对照组、imDC组比较均有显著统计学意义（P〈0．01）,能够刺激自体T细胞增殖（SI〉2．00）。结论：供者imDC能够诱导自体T细胞低反应,有望用来防治GVHD。     

调节性T细胞及间充质干细胞在急性移植物抗宿主病中的研究进展

急性移植物抗宿主病(acute graft versus host disease,aGVHD)的一线治疗方案为糖皮质激素,但药物治疗特异性差,会增加异基因造血干细胞移植(allogeneic hematopoietic stem cell transplantation,allo-HSCT)后感染和复发的风险,而且激素耐药性移植物抗宿主病的治疗效果欠佳,目前尚缺乏标准的二线治疗方案。近年来,随着对具有免疫调节活性细胞的认识,人们发现此类细胞在aGVHD的防治中可能具有独特的作用,因而应用免疫调节性细胞治疗aGVHD引起了广泛关注,其中以调节性T细胞(regulatory T lymphocyte,Treg)和间充质干细胞(mesenchymal stem cells,MSCs)的研究最为广泛。为更好地了解免疫调节性细胞调控aGVHD的机制以及其临床应用的可行性和有效性,该文主要就Treg和MSCs生物学特性以及Treg和MSCs在预防与治疗aGVHD中的作用作一综述。     

趋化因子及其受体介导的细胞迁移与移植物抗宿主病

移植物抗宿主病(graft-versus-hostdisease,GVHD)是同种异基因骨髓移植中的重要并发征。供者T细胞在输注入受者体内后迁移进入淋巴组织,识别受者同种异基因抗原,被受者抗原递呈细胞(antigenpresentingcell,APC)激活,进而活化、增殖分化,介导急性GVHD的发生。现有的研究已表明,活化的异体效应性T细胞经淋巴组织迁移进入黏膜组织以及实质性靶器官,如消化道、肝脏、肺脏和皮肤,进而造成这些器官和组织的损伤。因此,分子间相互作用尤其是趋化因子及其受体介导的效应性细胞的迁移是GVHD发生发展过程中关键的一环,受到了广泛的关注。进一步以趋化因子及其受体为靶标,亦可能形成有效的免疫生物学治疗,具有广阔的应用前景。     

细胞因子在急性移植物抗宿主病中的临床研究

目的:探讨细胞因子IL-21、SIL-2R在异基因造血干细胞移植(allo-HSCT)后急性移植物抗宿主病(aGVHD)发病机理中的作用。方法:观察20例Allo-HSCT患者aGVHD的发病情况,移植前后定期采集20例患者的外周血,采用双夹心酶联免疫吸附法(ELISA)检测其细胞因子IL-21、SIL-2R的浓度。结果:1.异基因造血干细胞移植后20例患者全部获得造血功能重建,中性粒细胞恢复到0.5×109/L及血小板恢复到20×109/L的中位时间分别为移植后13.5天及18天。2.发生aGVHD的患者,IL-21、SIL-2R浓度较移植前明显升高,IL-21、SIL-2R浓度在aGVHD阳性组明显高于aGVHD阴性组(P0.01)。结论:1.细胞因子IL-21、SIL-2R在aGVHD的发病中起重要的正向调节作用,检测异基因造血干细胞移植后患者血清的IL-21、SIL-2R水平有助于预测aGVHD的发生。2.IL-21、SIL-2R与感染无相关性。     

脐带间充质干细胞辅助治疗糖皮质激素耐药的慢性移植物抗宿主病5例并文献复习

目的:探讨脐带间充质干细胞输注治疗糖皮质激素耐药的慢性移植物抗宿主病的疗效和安全性。方法:5例糖皮质激素耐药的慢性移植物抗宿主病患者在原有免疫抑制剂治疗基础上联合脐带间充质干细胞治疗,2~4次为1个疗程,每次间隔1周。对患者进行定期随访观察其治疗效果、移植相关死亡、输注相关不良事件和复发率。结果:5例患者接受脐带间充质干细胞输注后2例获得完全缓解(CR)、2例获得部分缓解(PR),1例患者死亡。2例CR患者分别在脐带间充质干细胞治疗368、452d后停用免疫抑制剂,随访1~1.5年慢性移植物抗宿主病无复发;2例PR患者在脐带间充质干细胞治疗84、96d后开始进入免疫抑制剂减量阶段,目前病情仍稳定并存活。1例患者死于原发病无复发性肺部严重感染。治疗过程中及治疗后未观察到与治疗有关的副作用。新鲜制备脐带间充质干细胞的细胞活力(92%~95%)高于液氮冻存37℃水浴复苏细胞活力(72%~76%)。结论:脐带间充质干细胞辅助治疗可以改善糖皮质激素耐药的慢性移植物抗宿主病的临床症状且不增加恶性血液病复发率,新鲜制备间充质干细胞活性高于液氮冻存复苏细胞。     

同种异基因骨髓移植GVHD动物模型的建立及其病理生理学机制初探

目的：建立稳定的异基因骨髓移植GVHD（移植物抗宿主病）动物模型,并初步了解其病理生理学机制。方法：以BALB／c（H-2^d）雌性小鼠为受者,接受8Gy致死剂量的。Co全身照射后,输注雄性C57BL／6（H-2^b）供鼠的脾细胞和骨髓细胞,观察受鼠的体征、造血功能恢复及生存时间的变化,并进行病理学、嵌合体和T细胞亚群及相关细胞因子的检查。结果：模型组小鼠在移植后出现了典型的GVHD症状;肠、肝、脾、皮肤的病理学分析均属于Ⅳ度GVHD;嵌合体植入成功;以7、14和21d为检测时间点,发现模型组鼠体内T细胞亚群移植后较移植前CD3^＋CD4^＋T细胞数量减少,CD3＋CD8＋T细胞显著升高,CD4^＋和CD8^＋T细胞比例严重倒置,随着时间变化比值会逐渐升高,但仍然处于较显著的倒置水平;血清中IFN-γ、TNF-α在移植后＋7d表达显著增高,尤其是IFN-γ的表达在＋7d达峰值;IL-4和IL-10的水平在移植前后几乎没有变化。结论：建立了稳定的GVHD动物模型;此模型发病过程中,CD8^＋T细胞介导的CTL细胞毒性作用可能要大于CD4＋Th介导的细胞因子效应;IFN-γ、TNF-α炎症因子在GVHD的早期发挥重要作用;IL-4、IL-10的低水平分泌与急性GVHD的高发病率有关。     

大鼠异基因骨髓移植急性移植物抗宿主病模型的建立

目的建立较稳定的异基因骨髓移植急性移植物抗宿主病动物模型,为异基因骨髓移植后的急性移植物抗宿主病（aGVHD）的相关研究提供实验参照。方法以雄性SD大鼠为供鼠,雌性Wistar大鼠为受鼠,受体大鼠随机分成A、B、C、D、E 5组,移植当天所有受鼠均接受8.5 GY的全身照射（TBI）,于照射后4～6 h内,A组回输等量培养液,B组经尾静脉输注供鼠骨髓细胞（2×10^8个/kg）,C、D、E组分别回输供鼠骨髓细胞（2×10^8个/kg）＋不同比例的脾细胞。观察各组大鼠生存期、外周白细胞计数、及有无aGVHD的临床及病理表现。结果A组大鼠于15d内全部死亡,外周血白细胞计数明显减低,骨髓病理示造血组织减少,提示死于造血衰竭。B、C、D、E组大鼠外周血白细胞计数均有明显恢复,B组大鼠8只存活超过50 d,C、D、E组大鼠均于50 d观察期内死亡,并有aGVHD的临床表现及病理表现,但C组大鼠aGVHD的程度较轻且时间不集中,其中D、E组大鼠可于相对集中的时间内观察到典型aGVHD临床及病理。结论TBI预处理的方式是可行的,单纯输入异基因骨髓细胞不能引起明显的aGVHD,骨髓细胞与脾细胞1∶1及1∶1.5混合组均可作为异基因骨髓移植后理想的aGVHD动物模型。     

异基因免疫治疗中控制GVHD发生的研究进展

目前,异基因造血干细胞移植(allo-HSCT)已成为治疗某些恶性血液病的有效手段之一,然而伴随其而来的移植物抗宿主病(GVHD)是导致移植后患者死亡的重要并发症之一。因此,如何诱导移植后免疫耐受来控制GVHD,尤其是控制急性移植物抗宿主病(a GVHD)的发生及已成为研究的重要内容。GVHD的发生机制非常复杂,但最终为供者骨髓内的成熟T淋巴细胞识别受者体内的细胞表面的MHC-I和MHC-II及所递呈的多肽而导致供者的T细胞的激活、增殖并浸润到GVHD的靶器官如皮肤、小肠及肝脏并导致靶器官的损伤[1]。临床移植学和移植免疫学主要攻克的内容之一就是如何控制GVHD的发生发展。其预防和治疗是决定着同种异基因造血干细胞移植(allo-HSCT)是否成功的关键所在,移植个体是否长期存活的主要因素之一。本文章就导致GVHD现象的原因及最新进展做一总结。     

IL-10在输血相关性移植物抗宿主病小鼠模型中的免疫调节作用

目的:IL-10在输血相关性移植物抗宿主病小鼠模型中的免疫调节作用。方法:取BALB/c实验小鼠免疫活性淋巴细胞,分别输注于BALB/c小鼠(设为A组)及BALB/c裸鼠(设为B组),建立TA-GVHD模型,观察小鼠症状,HE染色判断小鼠肝、肺、小肠、皮肤病理变化情况;采用双夹心酶联免疫吸附法(ELISA)检测两组小鼠血清IL-10浓度;用逆转录聚合酶链反应法RT-PCR检测移植后外周血单个核细胞中IL-10的表达。结果:A组中2只死亡(12.5%),B组中3只死亡(18.75%),共5只死亡,29只存活,两组死亡率比较无明显差异(P>0.05)。B组小鼠累及肝、肺、小肠和皮肤病理损伤程度较A组严重;存活小鼠IL-10浓度较死亡小鼠明显升高(P2<0.05);存活小鼠IL-10 mRNA表达阳性率96.55%明显高于死亡小鼠(20.00%)。结论:IL-10在输血相关的移植物抗宿主病小鼠模型中发挥负向免疫调节--免疫抑制作用。     

Mycophenolate mofetil does not suppress the graft-versus-leukemia effect or the activity of lymphokine-activated killer (LAK) cells in a murine model

Background: Graft-versus-leukemia (GVL) effect is an essential component in the course of allogeneic stem cell transplantation (SCT). However, both prevention and treatment of established graft-versus-host disease (GVHD), including with drugs such as cyclosporine, can suppress GVL effects. Mycophenolate mofetil (MMF) is becoming a standard of care in SCT recipients for better prevention of GVHD as well as for promoting stem cell engraftment. Aims: To evaluate the effect of MMF, an immunosuppressive drug increasingly used for prevention of GVHD, on disease recurrence following SCT in a preclinical animal model. Since GVL effects may be also induced by alloreactive natural killer (NK) cells, the goal was to investigate the effects of MMF on the activity of lymphokine-activated killer (LAK) cells. Methods: MMF was administered by daily intraperitoneal injection starting at day 1 post-SCT. Cytotoxic LAK activity was measured by 5-h ³⁵S-release assay, and GVL was tested by the appearance of BCL1 leukemia in a semi-mismatched (C57BL/6 donors to [BALB/c × C57BL/6] F₁ recipients) murine model. Results: A dosage regimen of 28–200 mg/kg per day MMF had no negative effect on either cytotoxic LAK activity or GVL (as measured by finding of leukemic cells in recipient spleen by PCR or the appearance of clinical leukemia with adoptive transfer). Conclusions: These results suggest that MMF does not impair GVL effects or reduce LAK cell activity in mice.     

Elimination of leukemia in the absence of lethal graft-versus-host disease after allogenic bone marrow transplantation

Donor T cells are able to effect a graft-vs-leukemia (GVL) response but also induce graft-vs-host disease (GVHD) after allogeneic bone marrow transplantation. We used an AKR leukemia murine transplant model, analogous to human acute lymphoblastic leukemia, in which donor T cells expressed a thymidine kinase suicide gene, to test whether separation of GVL and graft-vs-host (GVH) responses was feasible by selectively eliminating alloactivated donor T cells at defined time points posttransplant. Under experimental conditions where untreated mice could not be cured of disease without dying from GVHD, mice transplanted with thymidine kinase-positive T cells and subsequently administered ganciclovir (GCV) could eliminate leukemia without lethal GVHD. Timing of GCV administration, donor T cell dose, and preexisting leukemia burden were observed to be critical variables. Eradication of leukemia without lethal GVHD in GCV-treated mice implied that the kinetics of GVL and GVH responses were asynchronous and could therefore be temporally dissociated by timely GCV administration. That this strategy was feasible in a murine leukemia model in which GVHD and GVL reactivity are tightly linked suggests that this approach may be relevant to the treatment of selected human leukemias where similar constraints exist. This strategy represents an alternative approach to separating GVL and GVH reactivity and challenges the current paradigm that separation of these responses is dependent upon the administration of donor T cells with restricted specificity for leukemia as opposed to host Ags.     

Macrophage inflammatory protein-2 (MIP-2)/CXCR2 blockade attenuates acute graft-versus-host disease while preserving graft-versus-leukemia activity

Allogenic bone marrow transplantation (BMT), an important treatment for hematological malignancies, is often complicated by graft-versus-host disease (GVHD). Suppression of GVHD is associated with the unwanted diminishment of the graft-versus-leukemia (GVL) response. The aim of this study was to maintain the benefits of GVL during GVHD suppression through isolated blockade of T-cell migration factors. To this end, we developed a murine model of B-cell leukemia, which was treated with BMT to induce GVHD. Within this model, functional blockade of MIP-2/CXCR2 was analyzed by observing proteomic, histologic and clinical variables of GVHD manifestation. Luminex assay of collected tissue identified several cytokines [granulocyte colony-stimulating factor (G-CSF), keratinocyte-derived chemokine (KC), macrophage inflammatory protein-2 (MIP-2), and interleukin-23 (IL-23)] that were upregulated during GHVD, but reduced by neutralizing the MIP-2/CXCR2 axis. In addition, donor T-cell blockade of CXCR2 combined with recipient administration of anti-MIP-2 caused a significant decrease in GVHD while preserving the GVL response. We propose that blocking the MIP-2/CXCR2 axis represents a novel strategy to separate the toxicity of GVHD from the beneficial effects of GVL after allogenic BMT.     

A crucial role for antigen-presenting cells and alloantigen expression in graft-versus-leukemia responses

Graft-versus-leukemia (GVL) response after allogeneic bone marrow transplantation (BMT) represents one of the most potent forms of immunotherapy against malignant diseases. Antigen-presenting cells (APCs) are crucial for the induction of graft-versus-host disease (GVHD), the most serious complication of allogeneic BMT, but their role in GVL responses is unclear. Using a series of clinically relevant mouse GVL tumor models, we found that APCs and alloantigen expression on tumors are crucial for GVL. Moreover, APCs of host origin predominated in GVL responses although donor APCs contributed as the acuity of tumor burden decreased.     

Donor APCs are required for maximal GVHD but not for GVL

Graft-versus-host disease (GVHD) is a major source of morbidity in allogenic stem cell transplantation. We previously showed that recipient antigen-presenting cells (APCs) are required for CD8-dependent GVHD in a mouse model across only minor histocompatibility antigens (minor H antigens). However, these studies did not address the function of donor-derived APCs after GVHD is initiated. Here we show that GVHD develops in recipients of donor major histocompatibility complex class I-deficient (MHC I(-)) bone marrow. Thus, after initial priming, CD8 cells caused GVHD without a further requirement for hematopoietic APCs, indicating that host APCs are necessary and sufficient for GHVD. Nonetheless, GVHD was less severe in recipients of MHC I(-) bone marrow. Therefore, once initiated, GVHD is intensified by donor-derived cells, most probably donor APCs cross-priming alloreactive CD8 cells. Nevertheless, donor APCs were not required for CD8-mediated graft-versus-leukemia (GVL) against a mouse model of chronic-phase chronic myelogenous leukemia. These studies identify donor APCs as a new target for treating GVHD, which may preserve GVL.     

Graft-versus-Host Disease Is Enhanced by Selective CD73 Blockade in Mice

CD73 functions as an ecto-5′-nucleotidase to produce extracellular adenosine that has anti-inflammatory and immunosuppressive activity. We here demonstrate that CD73 helps control graft-versus-host disease (GVHD) in mouse models. Survival of wild-type (WT) recipients of either allogeneic donor naïve CD73 knock-out (KO) or WT T cells was similar suggesting that donor naïve T cell CD73 did not contribute to GVHD. By contrast, donor CD73 KO CD4⁺CD25⁺ regulatory T cells (Treg) had significantly impaired ability to mitigate GVHD mortality compared to WT Treg, suggesting that CD73 on Treg is critical for GVHD protection. However, compared to donor CD73, recipient CD73 is more effective in limiting GVHD. Pharmacological blockade of A2A receptor exacerbated GVHD in WT recipients, but not in CD73 KO recipients, suggesting that A2 receptor signaling is primarily implicated in CD73-mediated GVHD protection. Moreover, pharmacological blockade of CD73 enzymatic activity induced stronger alloreactive T cell activity, worsened GVHD and enhanced the graft-versus-leukemia (GVL) effect. These findings suggest that both donor and recipient CD73 protects against GVHD but also limits GVL effects. Thus, either enhancing or blocking CD73 activity has great potential clinical application in allogeneic bone marrow transplants.     

CD4+ T cells in aged or thymectomized recipients of allogeneic stem cell transplantations

Background

CD4+CD25highFOXP3+ regulatory T (Treg) cells, which include thymus-derived and peripherally induced cells, play a central role in immune regulation, and are therefore crucial to prevent graft-versus-host disease (GVHD). The increasing use of allogeneic hematopoietic stem cell transplantation (allo-HSCT) for elderly patients with thymus regression, and our case of allo-HSCT shortly after total thymectomy, raised questions about the activity of thymus-derived Treg cells and peripherally induced Treg cells, which are otherwise indistinguishable.

Results

We found that despite pre-transplant thymectomy or older age, both naïve and effector Treg cells, as well as naïve and effector conventional T cells, proliferated in allo-HSCT recipients. Higher proportions of total Treg cells 1 month post allo-HSCT, and naïve Treg cells 1 year post allo-HSCT, appeared in patients achieving complete chimera without developing significant chronic GVHD, including our thymectomized patient, compared with patients who developed chronic GVHD.

Conclusions

Treg cells that modulate human allogeneic immunity may arise peripherally as well as in the thymus of allo-HSCT recipients.     

Donor CD8+ T cells mediate graft-versus-leukemia activity without clinical signs of graft-versus-host disease in recipients conditioned with anti-CD3 monoclonal antibody

Donor CD8(+) T cells play a critical role in mediating graft-vs-leukemia (GVL) activity, but also induce graft-vs-host disease (GVHD) in recipients conditioned with total body irradiation (TBI). In this study, we report that injections of donor C57BL/6 (H-2(b)) or FVB/N (H-2(q)) CD8(+) T with bone marrow cells induced chimerism and eliminated BCL1 leukemia/lymphoma cells without clinical signs of GVHD in anti-CD3-conditioned BALB/c (H-2(d)) recipients, but induced lethal GVHD in TBI-conditioned recipients. Using in vivo and ex vivo bioluminescent imaging, we observed that donor CD8(+) T cells expanded rapidly and infiltrated GVHD target tissues in TBI-conditioned recipients, but donor CD8(+) T cell expansion in anti-CD3-conditioned recipients was confined to lymphohematological tissues. This confinement was associated with lack of up-regulated expression of alpha(4)beta(7) integrin and chemokine receptors (i.e., CXCR3) on donor CD8(+) T cells. In addition, donor CD8(+) T cells in anti-CD3-conditioned recipients were rendered unresponsive, anergic, Foxp3(+), or type II cytotoxic T phenotype. Those donor CD8(+) T cells showed strong suppressive activity in vitro and mediated GVL activity without clinical signs of GVHD in TBI-conditioned secondary recipients. These results indicate that anti-CD3 conditioning separates GVL activity from GVHD via confining donor CD8(+) T cell expansion to host lymphohemological tissues as well as tolerizing them in the host.     

Rapid reconstitution of NK1 cells after allogeneic transplantation is associated with a reduced incidence of graft-versus-host disease

The balance between immunostimulation and immunoregulation in T cell immunity is achieved by maintaining specific ratios of Th1, Th2, Th3 and Tr1 cells. Here, we investigate levels of type 1(IFN-gamma; NK1), type 2(IL-13; NK2), type 3(TGF-beta;NK3) and regulatory(IL-10; NKr) cytokines in peripheral blood to assess the cytokine profiles of natural killer(NK) cells following human allogeneic hematopoietic stem cell transplantation(allo-HSCT). NK2 and NK3 cell expansion was observed after allo-HSCT; levels of NKr cells reached donor levels at day 15, though levels of NK1 cells were consistently lower than donor levels until day 60 after allo-HSCT. Multivariate analysis showed that a higher level of NK1 cells by day 15 was associated with a lower overall risk of acute graft-versus-host disease(GVHD)(HR 0.157, P=0.010) as well as II-IV acute GVHD(HR0.260, P=0.059). Furthermore, higher levels of NK1 cells by day 15 were correlated with lower rates of cytomegalovirus(CMV)reactivation(HR 0.040, 0.005–0.348, P=0.003). These results indicate that rapid reconstitution of NK cells, especially NK1 cells,can help prevent the development of GVHD as well as CMV reactivation after allogeneic transplantation.     

Differential Effect of MyD88 Signal in Donor T Cells on Graft-versus-Leukemia Effect and Graft-versus-Host Disease after Experimental Allogeneic Stem Cell Transplantation

Despite the presence of toll like receptor (TLR) expression in conventional TCRαβ T cells, the direct role of TLR signaling via myeloid differentiation factor 88 (MyD88) within T lymphocytes on graft-versus-host disease (GVHD) and graft-versus-leukemia (GVL) effect after allogeneic stem cell transplantation (allo-SCT) remains unknown. In the allo-SCT model of C57BL/6 (H-2^b) → B6D2F1 (H-2^b/d), recipients received transplants of wild type (WT) T-cell-depleted (TCD) bone marrow (BM) and splenic T cells from either WT or MyD88 deficient (MyD88KO) donors. Host-type (H-2^d) P815 mastocytoma or L1210 leukemia cells were injected either subcutaneously or intravenously to generate a GVHD/GVL model. Allogeneic recipients of MyD88KO T cells demonstrated a greater tumor growth without attenuation of GVHD severity. Moreover, GVHD-induced GVL effect, caused by increasing the conditioning intensity was also not observed in the recipients of MyD88KO T cells. In vitro, the absence of MyD88 in T cells resulted in defective cytolytic activity to tumor targets with reduced ability to produce IFN-γ or granzyme B, which are known to critical for the GVL effect. However, donor T cell expansion with effector and memory T-cell differentiation were more enhanced in GVHD hosts of MyD88KO T cells. Recipients of MyD88KO T cells experienced greater expansion of Foxp3- and IL4-expressing T cells with reduced INF-γ producing T cells in the spleen and tumor-draining lymph nodes early after transplantation. Taken together, these results highlight a differential role for MyD88 deficiency on donor T-cells, with decreased GVL effect without attenuation of the GVHD severity after experimental allo-SCT.