胸腺内注射异基因抗原诱导免疫耐受的实验研究

目的探讨胸腺内注射异基因抗原在建立特异性移植免疫耐受中的作用.方法自供体C57BL/6小鼠脾细胞中提取的H-2抗原,注入受体Balb/c小鼠胸腺内,1w后移植供体C57BL/6小鼠皮肤及无关供体C3H小鼠皮肤.观察皮肤存活时间,同时做单向混合淋巴细胞培养(mixedlymphocyteculture,MLC)、细胞介导的淋巴细胞毒(cellmediatelymphocytotoxic,CML)、迟发型超敏反应(delayedtapehypersensitivity,DTH)的检测.结果实验组移植皮肤平均存活时间(mediansurvivaltimes,MST)＞70d,对照组MST为12.6±1.69d,移植C3H皮肤的无关供体组MST为13.4±1.42d.耐受小鼠淋巴细胞对供体淋巴细胞刺激的反应性减弱,而对无关供体淋巴细胞的刺激呈正常反应,耐受小鼠对供体靶细胞的CML作用、DTH反应特异性降低.显示出胸腺内注射抗原诱导耐受的特异性.结论胸腺注射异基因H-2抗原可以诱导特异性皮肤移植耐受.     

大鼠胚胎胸腺和后肾原基联合异种移植与诱导免疫耐受的初步研究

目的 将大鼠胚胎胸腺与后肾原基联合移植至无胸腺裸小鼠,探讨联合移植能否重建受体细胞免疫功能并诱导受者对异种供者器官的特异性免疫耐受的关系.方法 从受孕第15天(E15)的Lewis大鼠胚胎中提取胸腺、后肾原基,分别植入BALB/c裸小鼠腹腔右肾包膜下及大网膜内.移植后第10周,行胸腺、后肾移植物的形态学检查及移植后肾的功能检测;并进行外周血T淋巴细胞流式细胞学检测、单向混合淋巴细胞反应(MLR)及皮肤移植试验.结果 移植后第10周,移植胸腺及后肾形态发育良好.移植后肾显示一定的排泄功能,联合移植受体双肾切除后的生存时间明显延长(P＜0.05).联合移植受体的外周血T淋巴细胞重建良好;其淋巴细胞对胸腺供体来源的Lewis大鼠脾细胞的刺激呈特异性低反应(P＜0.01);且胸腺供体来源的大鼠移植皮片平均存活时间明显大于C57BL/6小鼠、BN大鼠移植皮片存活时间(P＜0.01).结论 E15 Lewis大鼠胚胎胸腺、后肾原基联合移植至细胞免疫缺陷的裸小鼠,移植物可生长分化形成器官并发挥功能,受体裸小鼠能重建免疫功能,并有可能诱导对同源供体器官的特异性异种移植免疫耐受.     

卵清蛋白激发对肠道菌群失调小鼠T细胞功能亚群的影响

目的:探讨卵清蛋白(OVA)雾化吸入激发对抗生素致肠道菌群失调小鼠肺组织及脾脏中T淋巴细胞功能亚群的影响.方法:32只BALB/c小鼠随机分为4组:菌群失调组、菌群失调加激发组、激发组、对照组.于实验第14天采用流式细胞术(FCM)检测肺组织及脾脏中Th1、Th2、Th17以及CD4+CD25+Foxp3+调节性T细胞(Tregs)水平.结果:菌群失调加激发组小鼠肺组织中Th2、Th17细胞水平增高,脾脏中Th1、Th2、Th17均与对照组无差异;菌群失调组及菌群失调加激发组小鼠肺组织及脾脏中Tregs水平均降低.结论:抗生素致肠道菌群失调小鼠经卵清蛋白雾化吸入激发后,可产生Th2、Th17细胞优势的变应性气道反应,与Tregs调节功能不足可能有关.     

小白鼠胸腺发育的组织化学观察

本文观察了BALB/C小鼠从胚胎至成年胸腺发育分化的组织化学变化特征。1.胚胎胸腺皮质外带大淋巴细胞含有糖原。生后1～21 d,皮质内带淋巴细胞内可见很多糖原颗粒;以后减少,成年为阴性。2.胚胎16 d开始,胸腺皮质及髓质内均有大量ANAE阳性的淋巴细胞,以后反应性渐增,出生时已接近成年水平。在皮质的阳性淋巴细胞占皮质淋巴细胞总数的23.90±0.66%;在髓质的为髓质淋巴细胞总数的61.20±1.99%;3.SDH在胚胎16 d的胸腺淋巴细胞内出现,以后活性逐渐增强;4.5′-Nsae和ATPase在胚胎胸腺淋巴细胞为阴性;生后7 d开始,髓质内一部分淋巴细胞变为弱阳性,以后活性渐增强;5.AcP活性以吞噬细胞中最强,部分胸腺淋巴细胞为弱阳性。     

间充质干细胞联合胰岛移植对受体鼠T淋巴细胞亚群的影响

目的研究骨髓间充质干细胞(MSCs)与胰岛共移植时,探讨MSCs如何通过T淋巴细胞亚群发挥免疫抑制作用。方法 Balb/c小鼠骨髓MSCs,与C57LB/6小鼠脾脏分离的T淋巴细胞和Balb/c小鼠脾淋巴细胞共培养,监测对T淋巴细胞增殖能力和细胞周期影响。与C57LB/6小鼠来源的T淋巴细胞共培养,流式细胞术分析T淋巴细胞亚群的变化。用Balb/c小鼠的骨髓MSCs和胰岛联合移植到C57BL/6糖尿病模型鼠,流式细胞术分析受体鼠T淋巴细胞亚群的变化。结果 MSCs可明显抑制T淋巴细胞增殖能力,使T细胞滞留在G0/G1期。使Th1/Th2和Tc1/Tc2比值向Th2和Tc2倾斜,对初始和记忆T细胞具有明显的抑制作用。MSCs联合胰岛移植可使免疫排斥反应减轻。结论 MSCs可抑制T淋巴细胞的增殖,Th1/Th2和Tc1/Tc2比值向Th2和Tc2倾斜,下调初始和记忆T细胞,以发挥免疫抑制作用。     

EAE小鼠胸腺萎缩与疾病严重程度关系的初步探究北大核心CSCD

目的:研究EAE小鼠胸腺萎缩与疾病严重程度的关系。方法:MOG35-55肽免疫C57BL/6小鼠诱导EAE,分析EAE小鼠疾病严重程度与胸腺萎缩的关系,流式细胞分析胸腺CD4+CD8+双阳性细胞、CD4+CD8-、CD4-CD8+单阳性细胞与疾病严重程度的关系。结果:尾部无力小鼠胸腺淋巴细胞数为(20.25±3.49)×106个,双后肢无力小鼠胸腺淋巴细胞数为(4.93±0.85)×106个,双后肢瘫痪小鼠胸腺淋巴细胞数为(1.8±0.19)×106个,四肢完全瘫痪小鼠胸腺淋巴细胞数为(0.52±0.07)×106个,组间差异有统计学意义(P<0.05);EAE疾病越重,CD4+CD8+双阳性细胞在胸腺细胞中的比例越低,CD4+CD8-、CD4-CD8+单阳性细胞比例越高,不同疾病组间差异有统计学意义(P<0.05)。结论:EAE小鼠疾病严重程度与胸腺萎缩程度关系密切,EAE小鼠中活化T细胞的定向迁移可能导致胸腺萎缩。     

胸腺切除对小鼠胸腺功能及外周T淋巴细胞的影响

目的通过小鼠模型研究胸腺切除对免疫学功能的影响。方法将新生期及幼龄期BALB/c小鼠分别随机分为2组,每组20只:行开胸手术并切除胸腺为手术组;除不切除胸腺外其余操作同前为假手术组。然后将2组再分别随机分为2个亚组,每组10只:一组于术后1个月,另一组于术后2个月,分别通过实时定量PCR检测T细胞受体重排删除环(TREC)、流式细胞术检测外周血T淋巴细胞及其亚群评估胸腺功能及外周血T淋巴细胞的变化。结果手术组外周血T淋巴细胞总数及其亚群、TREC明显低于假手术组,差异有统计学意义(P0.01)。新生期与幼龄期比较以及术后1月与术后2月检测指标比较,差异无统计学意义(P0.05)。结论幼年个体在开胸手术中切除胸腺会造成术后T细胞免疫功能降低,其影响可能与手术时年龄无关,且长期存在。     

不同途径的供者淋巴细胞输注对移植物抗宿主病的影响

目的:观察髓腔内供者淋巴细胞输注(IBM-DLI)对异基因小鼠外周造血干细胞移植(allo-PBSCT)后移植物抗宿主病(GVHD)的影响.方法:雌性C57BL/6小鼠为受鼠,接受全身照射(TBI)预处理后,输注雄性BALB/c小鼠来源的经rhG-CSF动员后的外周造血干细胞,分别经尾静脉(IV)和髓腔内进行DLI,建立异基因GVHD模型,观察移植后小鼠的生存状态和GVHD发生情况,应用流式细胞仪检测受鼠体内嵌合体形成和CD4~+CD25~+调节性T细胞(Tregs)比例,酶联免疫吸附实验(ELISA)检测白细胞介素4(IL-4)、γ干扰素(IFN-γ)水平.结果:IBM-DLI组的受鼠GVHD发生比例和严重程度较IV-DLI组明显降低(P＜0.01);移植后第7天各组受鼠骨髓中供鼠来源的细胞比例均在95%以上;与IV-DLI组比较,脾细胞中Tregs比例在IBM-DLI组明显升高(P＜0.01),IBM-DLI组IL-4分泌增多,IFN-γ分泌减少 (P＜0.01).结论:与IV-DLI相比,IBM-DLI有利于减轻GVHD的发生,其机制可能与受鼠体内Tregs细胞比例增高以及Th细胞向Th2细胞分化有关.     

CD4+Foxp3+调节性T细胞表达升高提示免疫应答而非移植耐受

目的 探讨诱导CD4+Foxp3+调节性T细胞(regulatory T cells,Tregs)表达的机制及其在移植耐受中可能的作用.方法 构建新生移植耐受小鼠动物模型,分析移植耐受与同种异体反应性T细胞、Tregs表达及嵌合体的关系;运用过继转移实验、EGFP转基因小鼠,研究移植排斥过程中Tregs表达及抗原特异性.结果 新生耐受小鼠形成嵌合体,同种异体反应性T细胞被克隆清除,但Tregs表达与初始小鼠相同;同种异体反应性T细胞识别抗原诱导免疫反应,Tregs在移植排斥反应中表达升高,且不仅同种异体反应性Tregs表达升高,非同种异体反应性Tregs表达也升高.结论 Tregs在移植排斥中非特异性诱导产生,可能为一种负反馈免疫调控机制.     

胸腺形态与胸腺静脉的解剖学特点及其临床意义

目的:探讨胸腺形态与胸腺静脉的解剖学特点和临床意义。方法:回顾性分析1989￣2003年胸腺手术切除123例。将病例分为胸腺增生组和胸腺瘤组,观测胸腺形态、胸腺静脉的数目、走行、长度和直径。结果:术中见胸腺形态分5种形态:H型占65.9%,蝶型占14.6%,三角型占10.7%,条型占6.5%,多叶型占3.3%。胸腺静脉汇入部位变异较大,多汇入左无名静脉(占67.2%)。胸腺静脉长:胸腺增生组为(18.4±2.2)mm,外径(5.4±0.1)mm,胸腺瘤组为(18.8±2.4)mm,外径(5.5±0.1)mm,两组胸腺静脉长度与外径差异无统计学意义(P>0.05)。结论:了解胸腺形态、胸腺静脉的解剖学特点对胸腺手术具有临床意义。     

氟达拉滨联合瘤苗抗肿瘤生物治疗作用的实验研究

目的探讨氟达拉滨对小鼠CD4＋CD25＋Treg细胞的影响，同时研究其抗肿瘤作用。方法氟达拉滨或生理盐水分别腹腔注射10只小鼠，用流式细胞术检测CD4＋CD25＋Treg细胞相对量。氟达拉滨或生理盐水分别腹腔注射10只小鼠，4d后用丝裂霉素灭活的肿瘤细胞免疫小鼠，观察小鼠抗肿瘤的能力（观察肿瘤发生率和出瘤时间）；用乳酸脱氢酶杀伤实验进一步验证氟达拉滨可增强CTL的杀伤活性。结果氟达拉滨组CD4＋CD25＋Treg细胞占淋巴细胞百分比为（1．150±0．256）％，对照组为（1．488±0．270）％，氟达拉滨组明显低于对照组（P〈0．05）；氟达拉滨＋接种瘤苗组、生理盐水＋接种瘤苗组、氟达拉滨＋未接种瘤苗组和生理盐水＋未接种瘤苗组小鼠第13天肿瘤发生率分别为10％、30％、50％和70％，两两间差异均有统计学意义（P〈0．05）；氟达拉滨＋接种瘤苗组、生理盐水＋接种瘤苗组、氟达拉滨＋未接种瘤苗组和生理盐水＋未接种瘤苗组小鼠分别在接种后第13天、第10天、第8天和第5天发现出瘤现象；对照组的肿瘤生长曲线较为陡直，氟达拉滨组的生长曲线较为平缓。氟达拉滨联合瘤苗接种组和单纯瘤苗接种CTL的活性分别为24．425±13．544和17．575±10．260，两者间差异有统计学意义（P〈0．05）。结论低剂量氟达拉滨降低CD4＋CD25＋Treg细胞，使其抗肿瘤免疫作用增强，联合接种灭活瘤苗进一步增强抵抗肿瘤攻击的能力。     

自发性流产小鼠模型主动脉旁淋巴结CD45+CD86+细胞亚群分析

目的：检测主动脉旁淋巴结(PLN)CD45+CD86+细胞，用于间接分析小鼠母-胎界面局部免疫状况。 方法： CBA/J×DBA/2、未孕CBA/J雌鼠和CBA/J×BALB/c小鼠分别作为自发性流产模型（A组）、未孕对照（N组）和生育力正常对照（F组）。采用流式细胞术检测CD45+CD86+细胞在CD45+细胞中的百分率（简称CD45+CD86+百分率）和这些细胞的绝对数，其中单个核细胞从孕5.5、9.5和13.5 d小鼠PLN和孕13.5 d胎盘分离获得。为鉴定CD86+细胞所属类型，采用CD3、CD19和DX5分别作为T细胞、B细胞和NK细胞特异性标志物进行流式细胞检测。 结果： A组胚胎吸收率和绝对数(29.3%, 1.8±1.0)均显著高于F组(4.8%, 0.3±0.5, P<0.01)。相应地，A组孕13.5 d PLN CD45+CD86+细胞百分率和绝对数也均显著高于F组(分别为27.5%±14.0% vs 12.3%±7.1%和1 362±687 vs 615±353, P<0.01)。未孕CBA/J雌鼠PLN CD45+CD86+百分率为7.5%，与孕5.5 d A组小鼠相近(10.6%)，至孕9.5 d时显著升高至23.9%(与未孕鼠相比，P<0.01；与孕5.5 d小鼠相比，P<0.05)，并保持高水平直至13.5 d(27.5%)。相反，在CBA/J×BALB/c小鼠孕期未观察到这种趋势。 结论： CBA/J×DBA/2小鼠流产开始发生于孕9.5 d，此时CD45+CD86+细胞数增多，提示这些细胞与胚胎吸收相关。从PLN中分离淋巴细胞进行表型分析，有助于间接评价母-胎界面局部免疫状况。     

Immune correlates of virological response in HIV-positive patients after highly active antiretroviral therapy (HAART)

Correlates of immune reconstitution after highly active antiretroviral therapy (HAART) are not completely understood, in particular as far as viro-immunological discordant responses are concerned. HIV-positive patients on stable HAART for > or = 1 year were recruited. Viro-immunological responses were categorized according to positive or negative area under the curve (AUC) variations for HIV plasma viral load (pVL) and CD4+ T-cell counts measured at least every 4 months. The following parameters were evaluated: lymphocyte spontaneous apoptosis (LSA), intracellular Bcl-2 expression in both CD4-CD45RA+ and CD4-CD45R0+, IL-7 and IL-15 plasma concentrations, and lymphocyte TRECs levels. Sixty-one patients were enrolled. A significant inverse correlation was found between CD4+ T-cell count and pVL AUC (r = 0.45; p = 0.0003). Patients with pVL response had higher levels of Bcl-2 in CD4-CD45R0+ (mean 65,409 MESF vs. 54,018 MESF; p = 0.089) and higher IL-15 (mean 1.34 pg/mL vs. 1.05 pg/mL; p = 0.069, respectively). Higher LSA and lower TRECs levels were found in viro-immunological non-responder patients with respect to those who had viro-immunological response (mean 24.84% vs. 14.89%; p = 0.01, and mean 17,796 copies/10(6) cells vs. 29,251 copies/10(6) cells; p = 0.68, respectively). Virological suppression may allow Bcl-2 and IL-15 hyperexpression during incomplete immune-reconstitution phase, while more complete immune reconstitution appeared to be marked by both high TRECs and low LSA levels, possibly indicating both central and peripheral CD4+ T-cell repopulations at this stage.     

多聚次黄苷酸-胞苷酸诱发性小鼠流产模型CD200+CK7+滋养层细胞分析

目的：在多聚次黄苷酸-胞苷酸［poly (I∶C)］诱发性流产小鼠模型中研究CD200+CK7+细胞与胚胎吸收的关系。 方法:采用Balb/c×C57BL/6和Balb/c×Balb/c小鼠，在孕早期注射poly (I∶C)以建立诱发性流产模型，并采用流式细胞术检测胎盘CD200+CK7+/CK7+细胞百分率和CD200+CK7+细胞的绝对数，采用免疫组化法对CD200+细胞在母-胎界面的分布情况进行定位检测。 结果: 在每例检测104个细胞的情况下，poly (I∶C)处理组上述细胞百分率和绝对数均显著低于对照组(Balb/c×C57BL/6小鼠：6.3%±6.2% vs 36.1%±9.3%, P<0.01; 140±111 vs 1 941±809, P<0.01。Balb/c×Balb/c小鼠：8.5%±4.8% vs 26.1%±8.0%, P<0.01; 701±499 vs 1 886±1 112, P<0.05)。与此相应，poly (I∶C)处理组孕13.5 d的胚胎吸收率也显著增高(Balb/c×C57BL/6小鼠: 从9.1%升至37.0%, P<0.01; Balb/c×Balb/c小鼠: 从5.8%升至29.0%, P<0.01)。免疫组化法检测发现，这些CD200+细胞主要分布在胎盘和子宫交界处的胎盘组织中。 结论: 在母-胎界面CK7+细胞群中CD200分子适当水平的表达，对于维持小鼠妊娠免疫耐受过程可能具有重要意义。     

rhIL-11和rhG-CSF联合应用对小鼠外周血T细胞亚群比例影响

为观察rhIL 11联合rhG CSF动员小鼠外周造血干细胞时 ,外周血T细胞亚群的变化 ,使用rhIL 11联合rhG CSF动员C5 7BL/ 6小鼠外周造血干细胞 ,观察用药不同时间小鼠外周血白细胞变化 ,同时通过流式细胞仪测定外周血T细胞亚群的变化。结果发现 ,小鼠注射rhIL 11后 ,外周血WBC明显升高 (P =0 0 0 3) ;单独注射rhG CSF或联用rhIL 11后 ,外周血WBC于第 5天达峰值 ,分别由用药前的 (7 5 3± 1 6 5 )× 10 9/L、 (7 2 7± 1 4 8)× 10 9/L上升至 (2 7 12± 1 84 )× 10 9/L、 (2 8 98± 3 13)× 10 9/L ,均显著高于对照组 (P值均为 0 0 0 1) ,而rhG CSF组与联合组之间无显著性差异 (P >0 0 5 )。CD3+ 细胞比例在用药组均高于正常对照组 (P值均 <0 0 5 ) ,rhIL 11组CD3+ 细胞及CD4 + 细胞比例逐渐增高 ,于动员的第 5天达峰值 (P值均为 0 0 0 1) ,CD8+ 细胞的比例没有明显变化 (P >0 0 5 ) ;在rhG CSF组CD3+ 细胞也有明显增高 ,并于动员第五天达峰值 (P =0 0 0 1) ,CD4 + 细胞的比例没有明显变化 (P值均 >0 0 5 ) ,但CD8+ 细胞的比例明显升高 (P =0 0 0 1) ;在联合组中CD3+ 、CD4 + 、CD8+ 细胞的比例变化均有明显升高。结果证明 ,rhIL 11联合rhG CSF能明显提高外周血WBC ,增加CD3+ 细胞比例 ,同时rhIL 11     

抗CD20单抗在致敏受者造血干细胞移植中应用的实验研究

目的： 寻找促进异基因造血干细胞在致敏受者植入的策略研究,探讨抗CD20单抗在致敏受者造血干细胞移植的作用。方法：分别于移植前第14 d及第7 d予BALB/c小鼠输注C57BL/6小鼠的脾细胞建立致敏模型。实验组于移植前第11 d经尾静脉输注抗CD20单抗（美罗华）2 mg/mouse,对照组于移植前第11 d予输注RPMI-1640培养液 0.2 mL/mouse。于第0 d（移植当天）取部分小鼠分离得血清及脾细胞,并检测供者反应性抗体及CD19＋B细胞;部分小鼠予［60Co］致死量照射,4 h后予1×107 C57BL/6小鼠骨髓细胞进行移植,观察生存情况及血常规恢复情况。结果：实验组与对照组血清细胞毒性指数分别为（37.00±3.46）％和（51.80±3.49）％,差异显著（P<0.01）;2组的脾细胞CD19＋B细胞百分比分别为（17.32±3.02）％和（34.26±2.87）％,差异显著（P<0.01）。照射移植后2组受者均于14 d左右全部死亡,生存中位数分别为第13 d及第11 d,Log-rank检验2组间的差别无显著（P>0.05）。濒死动物血常规结果示三系减少,提示受者死于造血衰竭。结论：抗CD20单抗能杀伤受者B细胞,降低致敏程度,但实验中该单抗并不能有效促进异基因造血干细胞在致敏受者的植入。     

CD25+ immunoregulatory T-cells of donor origin suppress alloreactivity after BMT.

We have previously identified donor-derived Thy1+ alphabeta T-cell receptor (TCR)+ CD4+ CD8- regulatory T-cells that suppress GVH reactivity induced by donor leukocyte infusion (DLI) after BMT. These cells develop in the recipient thymus and may play a role in the maintenance of donor-host tolerance after allogeneic BMT. In the present study, we sought to further characterize the T-cells responsible for the regulatory cell activity in our model. Lethally irradiated recipient AKR mice (H-2k) received transplants of BM from CD25-deficient (-/-) C57BL/6 mice (H-2b). Recipients of CD25-deficient BM developed more severe GVHD after DLI than did recipients of normal BM, a result that indirectly suggests that CD4+ CD25+ regulatory T-cells are important to the suppression of GVH reactivity after allogeneic BMT. GVHD was accompanied by mortality, body weight loss, and elevated percentages of T-cells from the DLI in the peripheral blood in mice that received CD25-deficient BM compared to mice that received normal BM. Both CD40-CD40L and CD28-B7 costimulatory pathways have been implicated in the generation of CD25+ regulatory T-cells. Therefore, we tested whether deficiency in either of these pathways affected the activity of donor BM-derived regulatory T-cells. The absence of CD40L did not affect the regulatory T-cells (ie, recipient mice were still protected from DLI-induced GVHD). In contrast, use of marrow from CD28-deficient mice resulted in complete loss of suppression of GVH reactivity. Thus, CD28 but not CD40L was critical for the generation and/or activation of immunoregulatory T-cells that suppressed GVHD induced by DLI. Together, the results of these experiments suggest that CD4+ CD25+ regulatory T-cells suppress GVH reactivity after BMT and that CD28 expression is indispensable for the generation of these cells.     

Levels of Recent Thymic Emigrant Cells Decrease in Children Undergoing Partial Thymectomy during Cardiac Surgery

The human thymus is required for establishment of a T-cell pool in fetal life, but postnatal thymectomy is not known to cause immunodeficiency. T-cell emigration from thymus (thymic recent emigrants [TRECs]) is a continuous thymic-dependent process. We studied TREC levels pre- and post-partial thymectomy in children undergoing cardiac surgery. TRECs were quantitated by real-time PCR in peripheral blood lymphocytes of 24 children (0 to 12 years). TREC values were 47916 ± 9271 pre-partial thymectomy and 33157 ± 8479 post-partial thymectomy in 11 paired patients (P = 0.014). Interval between pre- and post-partial thymectomy was 8.8 days ± 5.8 days. Another group of 8 children had 30384 ± 9748 TRECs 16 days to 6 years post-partial thymectomy. There was a significant drop in TREC values post-partial thymectomy in the immediate postoperative period compared to prethymectomy TREC levels. While decreased thymic output may persist, the long-term implications were not evaluated in this patient population.     

Nonmyeloablative regimen preserves "niches" allowing for peripheral expansion of donor T-cells.

T-cell recovery following myeloablative preparatory regimens and cord blood transplantation in adult patients gen erally occurs between 1 and 3 years following allogeneic bone marrow transplantation. T-cell reconstitution may involve thymic education of donor-derived precursors or peripheral expansion of mature T-cells transferred in the graft. We measured quantitative and qualitative immunologic reconstitution, T-cell receptor spectratyping, and T-cell receptor excision circle (TREC) levels in adult recipients of umbilical cord blood transplants following a novel nonmyeloablative regimen. These results were compared to previously published results of similar patients receiving a myeloablative regimen and cord blood stem cells. With small numbers of patients treated so far, T-cells (CD3+) reached normal levels in adults 6 to 12 months following nonmyeloablative transplantation compared with 24 months in adults receiving a myeloablative regimen. At 12 months after transplantation, the numbers of phenotypically naive (CD45RA) T-cells were higher in those receiving the nonmyeloablative regimen. The T-cell repertoire in cord blood recipients treated with a nonmyeloablative regimen was markedly more diverse and robust compared with the repertoire in those receiving the myeloablative regimen at similar time points. TRECs (which are generated within the thymus and identify new thymic emigrants and those that have not divided) were detected 12 months after transplantation in the nonmyeloablative recipients, whereas TRECs were not detected in adults until 18 to 24 months in those receiving myeloablative regimens. Thus, in adults receiving a nonmyeloablative preparatory regimen, the quantitative and qualitative recovery of T-cells occurs through rapid peripheral expansion. The ability of patients receiving a nonmyeloablative regimen to recover within a few months suggests that the peripheral niches in which T-cells can proliferate are preserved in these patients compared to those receiving ablative regimens. Moreover, the presence of TREC-positive cells within 1 year suggests that thymic recovery is likewise accelerated in non myeloablative compared to myeloablative regimens.