125I粒子植入联合静脉化疗治疗Ⅲb期、Ⅳ期非小细胞肺癌的疗效

目的探讨放射性125I粒子组织间植入联合静脉化疗对Ⅲb期、Ⅳ期非小细胞肺癌(NSCLC)的疗效。方法Ⅲb期、Ⅳ期NSCLC患者按治疗方法不同分为2组。联合组(n=43)125I粒子植入3天后,联合TP(紫杉醇+顺铂)方案或GP(吉西他滨+顺铂)方案化疗;对照组(n=47)仅接受TP或GP方案化疗。比较2组治疗有效率、生存率和中位生存期。结果联合组和对照组Ⅲb期患者的近期局部总有效率分别为84.00%、48.28%,Ⅳ期患者有效率为72.22%、33.33%,组间差异均有统计学意义(P均0.05)。联合组和对照组Ⅲb期患者1、2年生存率分别为67.80%、36.00%和37.90%、13.83%,差异有统计学意义(P0.05),两组中位生存期分别为15.7个月、8.6个月;联合组和对照组Ⅵ期患者1、2年生存率分别44.44%、16.70%和22.22%、11.10%,差异无统计学意义(P0.05),两组中位生存期分别为8.9个月、6.0个月。结论 125I粒子组织间植入联合静脉化疗对Ⅲb期、Ⅳ期NSCLC患者的近期疗效良好,对于Ⅲb期NSCLC患者,联合治疗方案可提高患者的生存率。     

经动脉化疗栓塞序贯125I植入治疗中晚期肝癌疗效观察

【摘要】 目的 探讨经动脉化疗栓塞术(TACE)序贯125I放射性粒子植入治疗中晚期肝癌的临床疗效。方法 回顾性研究自2011年5月至2012年5月确诊为中晚期原发性肝癌的患者89例,A组45例(单纯TACE术),B组44例(TACE术后7~10天内序贯125I放射性粒子植入),125I放射性粒子植入严格遵从计算机三维治疗计划系统(TPS)的方案进行粒子布源。对比观察两组患者术后2、4个月的CT扫描显示的肿瘤局部控制有效率及术后6、9个月的生存率,两组局部控制率及术后6、9个月生存率比较采用卡方检验。 结果 随访术后第2、4月肿瘤局部控制有效率(CR+PR)A组是24.44%(11/45),17.78%(8/45),B组为54.55%(24/44),47.73%(21/44),P<0.05,两组差异比较具有统计学意义。A组术后6、9个月存活率分别是62.22%(28/45),42.22%(19/45),B组术后6、9个月存活率分别是90.91%(40/44),72.73%(32/44),两组同期P值均小于0.05,两组差异具有统计学意义。结论 经肝动脉化疗栓塞序贯125I放射性粒子植入治疗中晚期原发性肝癌临床疗效确切,提高生存率。     

胆道支架联合125I粒子条植入治疗恶性梗阻性黄疸

目的探讨胆道支架联合125I粒子植入治疗恶性梗阻性黄疸的疗效及安全性。方法收集我科收治的无法手术切除的恶性梗阻性黄疸患者47例,20例患者接受胆道支架植入治疗,另外27例给予胆道支架联合125I粒子条植入治疗,对所有患者随访1~20个月,记录患者的生存时间,并进行生存分析,于术后1、2周检测肝功指标水平变化。结果所有患者手术成功率100%,术后出现急性胰腺炎患者2例、胆道感染1例、胆汁性腹膜炎2例,未发生放射性泄漏、放射性肠炎等并发症,1个月后复查粒子条移位2例。单纯支架植入和支架联合125I粒子条植入患者的中位生存时间分别是158天(95%CI 135.96~180.04),279天(95%CI 189.59~368.41);平均生存时间分别是172天(95%CI 115.29~228.47)和284天(95%CI 224.53~342.80),两组差异均有统计学意义(P均0.05)。结论胆道支架联合125I粒子条植入安全可靠、疗效肯定,能有效延长患者的生存期。     

TACE联合放射性125I粒子植入治疗原发性肝癌合并门静脉癌栓

目的探讨对原发性肝癌合并门静脉癌栓患者行TACE联合放射性~(125)I粒子植入治疗的安全性和有效性。方法回顾性分析50例原发性肝癌合并门静脉癌栓患者,其中22例接受TACE联合放射性~(125)I粒子植入治疗(实验组),28例仅接受TACE治疗(对照组)。采用Kaplan-Meier法评价两组患者远期疗效;观察门静脉再通情况和不良反应。结果实验组和对照组中位生存期分别为8.7个月和6.0个月;两组累积生存率差异有统计学意义(P=0.012)。治疗后实验组与对照组门静脉再通、腹腔积液发生率差异有统计学意义(P均0.05),而恶心、呕吐、腹痛、腹泻、便秘、手足麻木发生率差异无统计学意义(P均0.05)。结论 TACE联合放射性~(125)I粒子植入治疗原发性肝癌合并门静脉癌栓安全可行。     

125I粒子条联合胆道金属支架植入术治疗恶性肝门区胆管梗阻

目的探讨~(125)I粒子条联合胆道金属支架植入术治疗恶性肝门区胆管梗阻的有效性及安全性。方法胆管梗阻患者38例,分为粒子组(n=18)和对照组(n=20)。粒子组接受~(125)I放射性粒子条联合胆道金属支架植入术,对照组接受单纯胆道金属支架植入术。观察治疗前后患者肝功能改善、血胆红素下降及手术相关并发症情况,比较2组胆道支架通畅时间及患者总生存时间差异。结果 2组术后1个月血清总胆红素、直接胆红素、碱性磷酸酶、谷氨酰转移酶、谷草转氨酶及谷丙转氨酶水平较术前均有显著性下降(P均0.05)。粒子组与对照组支架通畅时间分别为(192.94±28.59)天与(121.40±15.39)天。2组支架通畅率比较差异有统计学意义(χ~2=3.907,P=0.048);生存时间分别为(201.83±27.50)天与(142.25±15.46)天。2组生存率比较差异无统计学意义(χ~2=2.760,P=0.097)。并发症主要包括胆管炎、无症状淀粉酶升高、少量胆道出血等,2组间差异均无统计学意义(P均0.05)。结论 ~(125)I粒子条联合胆道金属支架植入术治疗恶性肝门区胆管梗阻安全、有效,可显著提高支架通畅率。     

放射性125I粒子支架适形治疗中晚期食管癌

目的探讨放射性~(125)I粒子支架适形治疗中晚期食管癌的临床价值。方法回顾性分析在我院接受支架治疗的中晚期食管癌患者68例,根据患者是否自愿接受放射性~(125)I粒子分为两组:普通支架组30例,粒子支架组38例,根据放射治疗计划系统(TPS)及肿瘤形态适形综合布源放射性粒子。比较两组支架置入成功率、并发症发生率、吞咽困难改善率及生存期情况。结果两组支架置入成功率100%,均未发生严重并发症,吞咽困难均缓解,两组间吞咽困难改善情况比较差异无统计学意义(P0.05),但粒子支架组平均生存期及中位生存期明显长于普通支架组(P均0.05)。结论中晚期食管癌患者治疗中,根据TPS及肿瘤形态适形综合布源不同活度放射粒子支架安全、可靠,可有效延长患者生存期,值得临床广泛应用。     

125I粒子条联合胆道支架治疗恶性梗阻性黄疸初步疗效评价

目的探讨125I粒子条联合胆道支架治疗恶性梗阻性黄疸的安全性及有效性。方法收集55例梗阻性黄疸患者,随机分为治疗组(支架+125I粒子条组)28例,对照组(单纯支架组)27例。均采用DSA引导下经皮肝穿刺途经行胆道支架植入术,治疗组同时将125I粒子条植入至支架与胆道壁间。观察两组患者介入术前及术后肝功能指标、术后并发症、支架通畅率及生存时间。结果 55例患者支架释放位置良好,手术过程成功,未出现支架移位现象。术后两组患者临床症状明显改善、均未出现胆道穿孔、出血等严重并发症。术后3、6个月时,两组患者间血清总胆红素、直接胆红素、间接胆红素、丙氨酸氨基转移酶、门冬氨酸氨基转移酶、胆汁酸的差异有统计学意义(P均0.05)。术后随访12个月,治疗组未发现放射粒子脱落。治疗组中位生存期为8个月,95%可信区间6.1~9.9个月,对照组中位生存期为5个月,95%可信区间3.3~6.7个月,二者差异有统计学意义(χ2=19.39,P0.05)。结论采用125I粒子条联合胆道支架治疗恶性梗阻性黄疸能够明显提高支架通畅时间,延长患者生存期。     

贲门癌术中植入~(125)I放射性粒子的临床疗效分析

目的探讨贲门癌术中应用125I放射性粒子的疗效。方法将接受手术治疗的52例晚期贲门癌患者,分为125I组(25例)和对照组(27例)。125I组患者术中胃左区域或外侵部位植入125I放射性粒子,对照组未植入125I放射性粒子,分析对比2组的疗效。结果 2组患者术后并发症发生率、住院时间、手术时间及排气时间均无统计学意义。125I组局部1~2 a复发率较对照组明显降低,P0.05,2组生存率差异无统计学意义。结论125I放射性粒子能有效减少贲门癌患者局部复发率,操作简单,不增加手术时间且安全可靠。     

通气导管辅助下125I支架植入治疗恶性气道狭窄

目的探讨局部麻醉及通气导管辅助下~(125)I粒子气管支架治疗恶性气道狭窄的疗效。方法回顾性分析于我科接受~(125)I粒子气管支架植入术治疗的恶性气道狭窄患者180例。分析~(125)I气管支架植入前、后患者气促评级、血氧饱和度(SaO2)及呼吸频率,术后随访患者的~(125)I支架情况、临床症状及生存情况。结果 180例均成功接受~(125)I粒子气管支架植入术,共植入~(125)I支架180枚,其中筒状支架132枚、"Y"型支架34枚、"L"型支架14枚。术后患者呼吸困难症状均有显著缓解。本组患者SaO2由术前的(80.60±3.87)%提高至术后的(94.31±3.40)%,差异有统计学意义(t=-30.52,P0.01);呼吸频率由术前的(29.36±3.20)次/分改善至术后的(19.29±2.19)次/分,差异有统计学意义(t=35.09,P0.01)。术后随访3~13个月,6例患者出现~(125)I支架再狭窄;患者生存期为49~401天,平均(182±94)天,患者60天生存率的估计值为0.99,180天生存率的估计值为0.65。结论局部麻醉及通气导管辅助下~(125)I气管支架植入术治疗恶性气道狭窄是安全、有效的方法。     

TACE分别联合放射性125I粒子植入与射频消融治疗乏血供肝癌

目的探讨TACE联合放射性~(125)I粒子植入与TACE联合经皮射频消融(RFA)治疗乏血供肝癌的临床疗效。方法回顾性分析46例乏血供肝癌患者资料,其中25例(30个病灶)接受TACE联合放射性~(125)I粒子植入治疗(A组),21例(27个病灶)接受TACE联合RFA治疗(B组)。比较两组疗效及并发症情况。结果治疗后3个月,B组临床有效率(RR)为96.30%(26/27),明显高于A组[86.67%(26/30),χ~2=8.694,P0.05];直径≤3cm的病灶中,A、B组的RR均为100%(8/8、10/10);在直径3~5cm的病灶中,A、B组的RR分别为81.82%(18/22)、94.12%(16/17),差异无统计学意义(χ~2=5.837,P0.05)。治疗后6个月,A、B组的RR分别为93.33%(28/30)、96.30%(26/27),差异无统计学意义(χ~2=3.422,P0.05);直径≤3cm的病灶中,A、B组的RR均为100%(8/8、10/10);直径3~5cm的病灶中,A、B组的RR分别为90.91%(20/22)、94.12%(16/17),差异无统计学意义(χ~2=2.716,P0.05)。两组术后并发症差异无统计学意义(P均0.05),均未出现严重并发症。结论 TACE联合放射性~(125)I粒子植入与TACE联合RFA均为乏血供肝癌安全、有效的治疗方法,TACE联合RFA相对近期疗效更优。     

Scintiscanning demonstration of thymoma: Comparative study on scintiscans using201Tl,67Ga and75Se

Thymus scintigraphy was performed using²⁰¹Tl-chloride,⁶⁷-Ga-citrate and⁷⁵Se-selenomethionine on 30 thymoma patients with or without myasthenia gravis. Mass negativity was observed in 6 out of 17 (35.3 per cent) and 3 out of 13 cases (23.1 per cent), respectively. A rate of 70 per cent (21 cases out of 30) of mass positivity was observed by thymus scan using²⁰¹Tl. With regard to the relation between thymus scan and cell type,²⁰¹Tl-scan exhibited a high rate of mass positivity, regardless of the cell type while the⁷⁵Sescan showed a trend toward mass positivity in epithelial cell predominant cases. With²⁰¹Tl, mass positivity was observed when the CPM/g ratio for tumors and blood exceeded 3.0. This trend can serve as an index for the suitability of supplementary chemo- and radiotherapies, as well as for prognosis in cases of relapse, and in those for whom excision was not complete.     

Inhibition of bone cell metabolism increases strontium-85 uptake

Summary Experiments have been performed on the canine tibia to investigate whether perturbation of the energy metabolism of bone cells can influence the short-term exchange of bone mineral. Simultaneous injection of three radioactive tracers,¹²⁵I-albumin,⁸⁵Sr, and⁸⁶Rb, into the tibial nutrient artery was followed immediately by measurement of the concentration of these tracers in the venous outflow from the bone for a period of 5 minutes. This procedure was performed before and after the injection of potassium cyanide into the bone. From the measured concentrations, extraction ratios for⁸⁵Sr and⁸⁶Rb with respect to¹²⁵I-albumin were calculated. It was found that net extraction after 5 minutes of⁸⁵Sr was significantly increased. This result indicates that efflux of ions from exchangeable mineral is dependent to a significant extent on the metabolic activity of bone cells.     

Resolving Erythrocytosis and Hypertension after Open Surgical Extirpation of Giant Renal Cyst Measuring 30 cm: Case Report

We previously described a method to measure GFR in conscious spontaneously voiding rats. This method circumvents the need for anesthesia and for bladder instrumentation. It's main principle is the correction of renal ¹²⁵I-iothalamate clearance for incomplete urine collection by the ratio of plasma and renal clearance of co-infused ¹³¹I Hippuran. A disadvantage of this technique is the requirement of an intra-arterial catheter for infusion of the renal function tracers. We therefore tested whether intraperitoneal infusion of ¹²⁵I-Iothalamate and ¹³¹I-Hippuran can be used for such a GFR measurement in conscious spontaneously voiding rats.

We found that during intraperitoneal administration, stable plasma levels of ¹³¹I-Hippuran could be obtained. However, urinary recovery of ¹³¹I-Hippuran was incomplete (66 ± 32%), leading to a significant overestimation of GFR by 140 ± 113% in comparison with the GFR measured by the intra-arterial technique. Thus intraperitoneal infusion of renal function tracers cannot replace intra-arterial infusion.     

Induction of transplantation tolerance by allogeneic donor-derived CD4(+)CD25(+)Foxp3(+) regulatory T cells

Several studies have shown that recipient-derived CD4(+)CD25(+)Foxp3(+) regulatory T cells (Tregs) are involved in transplantation tolerance. However, it is not clear whether allogeneic donor-derived Tregs are able to regulate T cell alloreactivity after solid organ allograft transplantation. Related studies in experimental bone marrow transplantation have shown that allogeneic donor-derived Tregs are capable of promoting early and long-term allogeneic hematopoietic engraftment, accompanied by tolerance to donor and recipient antigens. However, in these models, donor-derived Tregs are syngeneic with respect to the T responder cells. The role of Tregs in solid organ transplantation models where recipient-derived T responder and donor-derived Tregs are allogeneic has been scarcely studied. In order to determine whether allogeneic Tregs were able to regulate T cell alloreactivity, CD4(+)CD25(-) and CD8(+) T responder cells were cultured with stimulator dendritic cells in several responder-stimulator strain combinations (C57BL/6-->BALB/c, BALB/c-->C57BL/6 and C3H-->BALB/c) in the presence of responder-derived, stimulator-derived or 3rd-party-derived Tregs. Then, the frequency of IFN-gamma+ alloreactive T cells was determined by means of ELISPOT assay. The results of this study demonstrate that, regardless of the responder-stimulator strain combination, both responder-derived and stimulator-derived Tregs, but not 3rd-party-derived Tregs, significantly inhibited CD4(+) and CD8(+) T cell alloreactivity. The effect of allogeneic stimulator-derived Tregs was dependent on IL-10 and TGF-beta and reversed by exogenous IL-2. In vivo experiments in nu/nu recipients reconstituted with CD4(+)CD25(-) T responder and Tregs showed that recipient and donor-derived, but not 3rd-party-derived Tregs, significantly enhanced skin allograft survival. Importantly, T cells from both recipient-derived and donor-derived Treg-reconstituted nu/nu recipients exhibited donor-specific unresponsiveness in vitro. These results show that allogeneic donor-derived Tregs significantly inhibit T cell alloreactivity and suggest their potential use in the induction of transplantation tolerance.     

Radionuclide Therapy of Bone Metastases

The skeleton is a potential metastatic target of many malignant tumors. Up to 85% of prostate and breast cancer patients may develop bone metastases causing severe pain syndromes in many of them. In patients suffering from multilocular, mainly osteoblastic lesions and pain syndrome, radionuclide therapy is recommended for pain palliation. Low-energy beta-emitting radionuclides ((153)samarium-ethylenediaminetetrameth-ylenephosphonate (EDTMP) and (89)strontium) deliver high radiation doses to bone metastases and micrometastases in the bone marrow, but only negligible doses to the hematopoietic marrow. The response rate regarding pain syndrome is about 75%; about 25% of the patients may even become pain free. The therapy is repeatable, depending on cell counts. Concomitant treatment with modern bisphosphonates does not interfere with the treatment effects. Clinical trials using a new, not yet approved nuclide ((223)Radium) and/or combinations of chemotherapy and radionuclides are aiming at a more curative approach.     

Matriderm versus Integra: a comparative experimental study

Aim

To compare engraftment rates and vascularisation in a rat model using either Integra Artificial Skin^® or Matriderm^®.

Methods

Matriderm^® and the dermal part of Integra^® were compared in a two-step procedure including matrix implantation and subsequent epidermal grafting. Neonatal rat epidermis was used as coverage to test for rapid and complete take.

Results

Efficiency and quality of vascularisation expressed by take rate of epidermis, and thickness of resulting neodermis, were identical for both matrices.

Conclusion

This first comparison of Matriderm^® with Integra^® in a rat model revealed no major differences in engraftment rates or vascularisation.     

Bone resorption measurement with unusual bone markers: Critical evaluation of the method in phosphorus-deficient and calcium-deficient growing rats

An in vivo method to evaluate bone resorption in rats, by using unusual bone seekers not dependent on renal tubular transfer, is described and a critical evaluation of the method is made. In our experimental conditions,⁸⁵Sr and¹⁷⁷Lu are virtually exclusively localized in bone whereas²³⁷Np remains unchanged in different soft organs, so that the concomitant use of these markers can be used for measuring bone resorption. If osteolysis occurs 21 days after the injection of these markers, under our experimental conditions, any increase in the urinary excretion of¹⁷⁷Lu and²³⁷Np represents a rise in bone resorption, whereas an increase in Sr excretion reflects both bone and renal tubular events. According to our bone localization studies, the enhancement of Lu and Np excretion reflects primarily an increase in cortical bone resorption localized at the endosteal (Lu) and at the periosteal (Np) surfaces respectively. In addition, strontium is considered to be the marker of mineral resorption whereas Lu and Np, under our experimental conditions, would reflect the organic bone resorption. This method is tested in phosphorus-deficient rats and in calcium-deficient rats which exhibit disturbances of calcium metabolism at both the bone and kidney levels. In agreement with previous investigations, the use of these bone markers to evaluate osteolysis shows: (a) after a 1-week phosphorus deficiency, a slight increase in cortical bone resorption with a simultaneous fall in calcium and strontium renal tubular reabsorption, and (b) after a 1-week calcium deficiency, a high rise in cortical bone resorption with a simultaneous increase in the renal tubular reabsorption of calcium and strontium.     

Prognostic value of peripheral blood T lymphocyte subsets in clear cell renal cell carcinoma

BackgroundTo date, few studies have evaluated the role of peripheral blood T lymphocyte subsets in patients with clear cell renal cell carcinoma (ccRCC). Here we measured the levels of peripheral blood T lymphocyte subsets and evaluated its prognostic value in ccRCC.MethodsData from 122 patients with RCC from January 2018 to January 2020 were collected. Preoperative peripheral blood T lymphocyte subsets and medical records were analyzed. Kaplan-Meier cures and log rank test were used for analyzing overall survival (OS). Univariate and multivariate survival analyses were underwent by performing the Cox proportional hazards models. Correlations were tested by Pearson’s correlation analysis.ResultsOf 122 patients, a total of 80 ccRCC patients was enrolled. Patients with low CD3⁺ T cells and low CD4⁺/CD8⁺ ratio displayed a worse OS than patients with high CD3⁺ T cells and high CD4⁺/CD8⁺ ratio (P=0.029 and 0.002, respectively). Multivariate analyses showed CD3⁺ T cells and CD4⁺/CD8⁺ ratio were independent predictive factors for the OS (HR: 0.295, 95% CI, 0.091–0.956; P=0.042 and HR: 0.244, 95% CI, 0.065–0.920; P=0.037, respectively). Moreover, NLR negatively correlated with both levels of CD3⁺ T cells and CD4⁺/CD8⁺ ratio (P<0.001, r=−0.398 and P=0.012, r=−0.280, respectively).ConclusionsThe findings of our study suggest that preoperative CD3⁺ T cells and CD4⁺/CD8⁺ ratio in peripheral blood are independent predictors for patients with ccRCC.     

Uptake of45calcium and85strontium by bone in tissue culture

Embryonic chick calvaria were cultured alive and after killing by various procedures. The uptakes of⁴⁵Ca and⁸⁵Sr were measured and it was found that both live and dead calvaria discriminated against strontium in favour of calcium. The discrimination in live bone at 37° was usually higher than that in dead bone or that in live bone cultured at 4°. However, discrimination did not approach the physicochemically predicted level, which suggests that discrimination against strontium is modified by the nature of the bone crystals and their environment.

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Zusammenfassung Calvarien von Kückenembryonen wurden lebend oder nach Abtöten mittels verschiedener Techniken gezüchtet. Die Aufnahme von⁴⁵Ca und⁸⁵Sr wurde gemessen, und es zeigte sich, daß sowohl die lebenden wie die toten Calvarien Calcium gegenüber Strontium vorzogen. Die Bevorzugung war im allgemeinen im lebenden Knochen bei 37° höher als im toten Knochen oder im lebenden, bei 4° gezüchteten Knochen. Jedoch erreichte diese Bevorzugung nicht den anhand physikochemischer Überlegungen vorausgesagten Grad. Dies läßt vermuten, daß die Calciumbevorzugung gegenüber Strontium durch die Natur der Knochenkristalle und deren Umgebung modifiziert wird.

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Résumé Des calottes craniennes d'embryons de poulet sont cultivées à l'état vivant et après mortification selon divers procédés. L'absorption de⁴⁵Ca et⁸⁵Sr est mesurée et il apparait que les calottes vivantes et mortifiées prennent du calcium au détriment du strontium. Cette action au niveau de l'os vivant à 37°, est généralement plus intense que celle observée au niveau de l'os mortifié ou celle de l'os vivant cultivé à 4°. Cependant cette absorption préférenttielle n'avoisine pas les concentrations prévues par la physico-chimie, ce qui laisse penser que l'action anti-strontium est modifiée par la nature des cristaux osseux et leur environnement.

     

Induction of transplantation tolerance—the potential of regulatory T cells

Solid organ transplantation is widely accepted as an effective treatment for end organ failure. Although the treatment with immunosuppressive drugs has undoubtedly greatly improved graft survival, chronic rejection still has considerable impact on long term outcome. This, together with the undesirable side effects associated with life long treatment with immunosuppressive drugs, have significant implications for long term outcomes.In a small number of patients, drug non-compliance as well as controlled reduction or removal of maintenance immune suppressive drug therapy has led to the uncovering of a tolerant state. The challenge of achieving improved monitoring of all transplant patients may allow tailoring of immunosupression in a proportion of recipients thereby increasing the opportunities for the induction of specific unresponsiveness to donor alloantigens in the future. The immune system using several mechanisms to both induce and maintain tolerance to alloantigens, including the deletion of allo-reactive T cells, the induction of anergy, clonal exhaustion, ignorance and active suppression (immunoregulation) of allo-responses. A minor subpopulation of CD4⁺ T cells, regulatory or suppressor CD4⁺ T cells that co-express the cell-surface molecule CD25 (IL2 α subunit) at a high level may play a major role in the maintenance of specific unresponsiveness and operational tolerance to donor antigens in vivo. Intensive investigation of these cells in recent years has started to uncover the mechanisms of active suppression by regulatory T cells in this setting.