异体皮在烧伤创面中的应用

异体皮在烧伤创面中的应用高俊明综述（山西省人民医院烧伤整形科太原０３００１２）关键词灼伤移植，异体外科皮瓣中图号Ｒ６４４在大面积深度烧伤中，由于自体皮源不足，不能尽快恢复破坏的皮屏障，使体液丢失，细菌侵入，引起感染和一些并发症，加之烧伤后机体抵抗力和...

尸体肾移植13例次的回顾与分析

１９９２年１２月～１９９６年４月的五年间共完成同种异体肾脏移植１３例次，从本组临床资料的回顾性分析显示：①高质量的取肾与植肾手术是预防急性肾功能衰竭，提高存活率的关键，②严格选择供、受者和充分术前准备是减少术后并发症。

福尔马林储骨的移植实验

用家兔14只，以桡骨中段10mm骨缺损作为实验模型，右侧植入同种异体福尔马林储骨为实验组，左侧植入酒精储骨作为对照组。于术后2、4、8、10、12周取材，作X线片和普通光镜观察，结果显示：福尔马林储骨移植术后4周缺损区有大量新骨形成，骨质增生活跃。8周时移植骨大部分被新生骨替代。12周时骨缺损基本愈合。结果表明，经福尔马林处理后的同种异体骨有较好的生物相容性，能引导骨生长，从而为推广尸体骨移植的临床应用，简化骨处理步骤提供了实验依据。

液态氮冷冻保存对异种神经移植后神经再生的影响

将成年日本大耳兔的胫神经在液态氮中保存４周或４０周，经反复冰冻、融解５次后移植至Ｗｉｓｔａｒ大白鼠的坐骨神经中。异种神经移植术后８、１２、２４周可观察到宿主的再生神经纤维从近段坐骨神经越过近端吻合部长入异种移植神经，继而越过远端吻合部向远段坐骨神经延伸。用体视学方法对异种神经移植段再生神经纤维的ＡＡ、ＮＡ和ＡＡ／ＮＡ测定和比较表明：异种神经在液态氮中保存４周和４０周后再移植，不影响宿主神经纤维的再生。

Massive allograft replacement in management of bone tumors

Objective： To evaluate the functional outcome and complications of allograft replacement in management of bone tumors. Methods： Between March 1992 and September 2002, 164 patients underwent bone tumor resection and massive allograft reconstruction of bone defects. The length of the resected part ranged from 5-35 cm. The resections were classified as marginal or wide resections of the tumor on the basis of the Musculoskeletal Tumor Society staging system. Fresh-frozen allografts were employed as osteoarticular grafts （n = 95）, hemi-condylar （n = 15）, massive （n = 23）, allograft-prosthesis composite （n = 12）, intercalary grafts （n = 15） or hemi-pelvic grafts （n = 4）. Most of the lesions were osteosarcoma and giant cell tumor of bone and located in proximal and distal femur, proximal tibia and humerus. Results： At a median follow-up of 47 months （range, 12 to 168 months） after the operation, 154 of the patients in the study were free of disease and 10 died of disease. Twenty-one （12.8%） patients had local recurrence and 38 （23.2%） nonunion. Late complications included 11 （6.7%） fractures of the allograft and 18 （11.0%） infections of the graft, instability of the joint in the form of subluxation was noted in 13 （7.9%） patients. Ten extremities were amputated due to local recurrence or severe infection. Conclusion： AIIografts can be used for reconstruction of bony defects after tumor resection. AIIograft has nearly similar shape, strength, osteo-inductivity and osteo-conductivity with host bone. AIIograft implantation is a high complication reconstruction method, and the dsk of recurrence increases when less surgical margin achieves.

Intrathymic inoculation of donor liver specific antigen alleviates rejection of liver allotransplantation

Use and effects of liver specific antigen in orthotopic liver transplantations were researched in this study. Group I:syngeneic control (Wistar to Wistar); Group II:acute rejection (SD to Wistar ); Group III: Thymic inoculation of SD rat LSA day 7 before transplantation. The observation of common situation and survival time, rejection grades, NF κB activity of splenocytes and IL 2mRNA expression of grafted liver were used to analyze acute rejection severity and immune state of animals in different groups. The common situation of group I was very well after transplantation and no signs of rejection were found. Recipients of group II lost body weight progressively. All dead within day 9 to day 13 posttransplantation; median survival time was 10.7 ±0.51 days. It was an optimal acute rejection control. As for group III, 5 out of 6 recipients survived for a long time and common situation was remarkably better than that of group II. Its rejection grades were significantly lower than that of group II( P <0.05). NF κB activity was only detected in group I at day 5 and day 7 after transplantation, whereas high activity of NF κB was detected at all time points in groupII and the low NF κB activity detected in group III was significantly lower than that of group II ( P <0.05). No IL 2mRNA expression was detected at any time point in group I,whereas high level expression was detected at all time points in group II and the low level expression only detected at day 3 in group III was significantly lower than that of group II ( P <0.05). Conclusion: LSA is an important transplantation antigen which is involved directly in the immunorejection of liver transplantation. We report here for the first time that intrathymic inoculation of LSA can alleviate the rejection of liver allotransplantation; and that grafts can survive for a long time thereby, thus leading to a novel way to achieve liver transplantation immunotolerance.

Resveratrol prolongs allograft survival after liver transplantation in rats

AIM： To study the immuno-modulatory effect of resveratrol （RES） on allograft rejection after liver transplantation in rats. METHODS： Male Sprague-Dawley （SD） rats were selected as donors and male Wistar rats as recipients for a rejection model. The recipients were divided into four groups after orthotopic liver transplantation （OLTx）. In the RES A, B, and C groups, RES was given intra-peritoneally once a day （25, 50, and 100 mg/kg, respectively） after OLTx, whereas in the control group, vehicle buffer was given intra-peritoneally once a day. The survival time, serum chemistry, production of cytokines, activation of transcription factor NF-kB, and histopathologic findings were then compared among these groups. RESULTS： The mean survival time after OLTx in the RES C group was significantly longer than that in the control group （16.7＋-1.2 d ,vs9.3＋-0.6 d, P〈0.01）. On the 7th posttransplant day the serum albumin level significantly improved in the RES C group, the serum total bile acid and alanine aminotransferase （ALT） levels were significantly lower in the RES C group, the serum IL-2 and INF-y levels were significantly lower in the RES C group, and the activation of transcription factor NF-kB in peripheral blood T lymphocytes was significantly suppressed in the RES A, B, and C groups in comparison to those in the control group. On the 7^th post-transplant day, a histological examination revealed apparent difference in the severity of rejection between the RES C group and control group. CONCLUSION： RES has an immuno-suppressive property as well as protective effect on hepatocytes under allograft rejection. It might serve as a novel agent for reducing the severity of hepatic allograft rejection in rats.

EXPRESSION OF ICAM-1 AND LFA-1 MOLECULES IN RELATION TO RENAL ALLOGRAFT REJECTION IN RATS

Objective.The purpose of this study was to assess the renal graft expression of ICAM 1(intercellular adhesion molecule 1) and LFA 1(lymphocyte function associated antigen 1)molecule with relation to graft rejection. Methods.Rat kidney transplantation was performed according to the procedure of Kamada with some modification.Experimental rats were divided into 5 groups.The survival time of recipient rats and function of grafts after renal transplantation were observed.The sections of renal graft were stained for monoclonal antibody ICAM 1 and LFA 1, and then quantification of ICAM 1 and LFA 1 expression was accomplished by computer image analysis. Results.ICAM 1 and LFA 1 increased significantly in the renal allograft rejection group as compared with the non rejection groups(P<0 05). Conclusion.Both biopsy of renal graft and monitoring of ICAM 1 and LFA 1 are useful tools in diagnosing and treating acute rejection.

The Anti—tumor Effects of an Anti—CD71 Chimeric Antibody in Vitro and Its Distribution in a Tumor Xenograft Model

Objective To investigate the anti-tumor effects in vitro and in vivo distribution of the human/murine chimeric antibody (D2C). Methods The CD71 positive target cells (K562, GEM and SMMC7721) and the effector cells, freshly isolated human PBMC, with the ratio of target cells to effector cells 1:50, were incubated in various dilutions of D2C antibody ( Ab) . Antibody dependent cytotoxicity (AD-CC) was tested by using an LDH-release assay. Instead of effector cells, complement was added to the target cells (GEM, SMMC-7721) with various dilutions of D2C Ab. A method of counting death cells was used in complement dependent cytotoxicity (CDC) assay. Tumor localization and distribution of the chimeric antibody (D2C) were observed by labeling the chimeric Ab with radioiodine(131I) and injecting it into nude mice (Balb/c nu/nu) transplanted with human hepatocellular carcinoma cells (SMMC-7721).Results A significant ADCC was observed with the increased concentration of the D2C Ab. Cytolysis of CD71-positive target cells by the D2C Ab was found in the presence of fresh rabbit complement. Labeled D2C administered by intraperitoneal as well as tumor regional injection, was visualized by SPECT. The distribution of D2C Ab in murine organs and tissues showed that non-specific binding was lower following tumor regional administration than when the antibody was administered by an intraperitoneal injection. The human/murine chimeric antibody (D2C) has in vitro anti-tumor effects and can exert its effects in specific tumor localization. Its distribution and local effects in vivo can be detected by radioimmunoimaging.Conclusion CD71 human/murine chimeric antibody showed marked killing of tumor cells in vitro, and specific recognition and high affinity binding to tumor tissue in vivo

Dynamization of retrograde interlocking intramedullary nail for nonunion of distal femoral intercalary allograft reconstruction:a case report and literatures review

Intercalary allograft reconstruction offers a joint-sparing reconstructive option, but nonunion is a devastating complication. In this article, we want to share our experience of proper dynamization of interlocking intramedullary nail for nonunion after proximal femoral intercalary allograft reconstruction. In this report, a 19-year-old girl was diagnosed proximal femoral fibroblast osteosarcoma （Enneking lib）. After neoadjuvant chemotherapy, she underwent proximal femoral intercalary allograft reconstruction fixed by retrograde interlocking intramedullary nail. At her follow-up point of one year postoperatively, nonunion was observed in the proximal host-allograft junction. Therefore she underwent the second surgery of dynamization of the interlocking intramedullary nail. After 12 months＇ partial and full weight bearing exercise, bone union occurred. Our early observations show that dynamization of interlocking intramedullary nail can still be a useful means to treat nonunion of host- allograft junction if the local condition of the host and allograft bone are good enough.

CD28/B7-MEDIATED COSTIMULATION IS REQUIRED FOR PARATHYROID GLAND ALLOGRAFT REJECTION IN RATS

The activation of T cells to differentiate and to proliferate is an essential step in the immune response to antigen, especially in cell mediated acute allograft rejection. Besides the interaction of CD3/TCR complex with Ag/MHC complex presented on antigen presenting cells, a complete T cell activation and proliferation requires a second costimulatory signal. The interaction of CD28/CTLA 4 and B7 is a major costimulatory pathway for T Cell activation. Inhibition of this pathway results in development of antigen specific unresponsiveness and clonal anergy.In present study,the biologic function of anti CD28 monoclonal antibody and its Fab fragment were investigated in vitro and in vivo.The results indicate that mAbCD28 and its Fab fragments could promote the functional recovery of allografts and prolong the graft survival,but could not reverse the acute rejection or induce transplantation tolerance in the rat PTG allograft model. We also found that peripheral TNF α level and NK cell activity were suppressed in the presence of mAbCD28 and its Fab fragments for a relatively long time after PTG transplantation.

TWO-YEAR OBSERVATION OF A RANDOMIZED TRIAL ON TACROLIMUS-BASED THERAPY WITH WITHDRAWAL OF STEROIDS OR MYCOPHENOLATE MOFETIL AFTER RENAL TRANSPLANTATION

Objective To evaluate the safety and feasibility of steroid or mycophenolate mofetil （MMF） withdrawal from tacrolimus-based immunosuppressant regimen in renal allograft recipients. Methods A cohort of 45 patients following cadaveric renal allograft transplantation were randomly divided into 3 groups based on the regimen of combination of tacrolimus, steroid, and MMF： triple therapy group, steroid withdrawal group, and MMF withdrawal group. During 2 years, survival of patients and allografts, clinical acute rejection, adverse events, hepatic and renal allograft function, and blood lipids were monitored to evaluate the safety and feasibility of steroid or MMF withdrawal after renal transplantation. Results During two-year observation, steroid or MMF was successfully withdrawn from immunosuppressant regimen based on tacrolimus without any clinical acute rejection renal allografts kept excellent function. Some adverse events among groups. Patient and graft survival rates were 100% and all the occurred and there were no significant differences Conclusion Withdrawal of steroid or MMF in low-immunological-risk renal allografts treated with tacrolimus-based immunosuppressant regimen can be achieved with no increased risk of acute rejection.

Generation of human/rat xenograft animal model for the study of human donor stem cell behaviors in vivo

AIM： TO accurately and realistically elucidate human stem cell behaviors in vivo and the fundamental mechanisms controlling human stem cell fates in vivo, which is urgently required in regenerative medicine and treatments for some human diseases, a surrogate human-rat chimera model was developed. METHODS： Human-rat chimeras were achieved by in utero transplanting low-density mononuclear cells from human umbilical cord blood into the fetal rats at 9-11 d of gestation, and subsequently, a variety of methods, including flow cytometry, PCR as well as immunohistochemical assay, were used to test the human donor contribution in the recipients. RESULTS： Of 29 live-born recipients, 19 had the presence of human CD45^＋ cells in peripheral blood （PB） detected by flow cytometry, while PCR analysis on genomic DNA from 11 different adult tissues showed that 14 selected from flow cytometry-positive 19 animals possessed of donor-derived human cell engraftment in multiple tissues （i.e. liver, spleen, thymus, heart, kidney, blood, lung, muscle, gut and skin） examined at the time of tissue collection, as confirmed by detecting human 132- microglobulin expression using immunohistochemistry. Tn this xenogeneic system, the engrafted donor-derived human cells persisted in multiple tissues for at least 6 mo after birth. Moreover, transplanted human donor cells underwent site-specific differentiation into CK18-positive human cells in chimeric liver and CEHS-positive human cells in chimeric spleen and thymus of recipients. CONCLUSION： Taken together, these findings suggest that we successfully developed human-rat chimeras, in which xenogeneic human cells exist up to 6 mo later. This humanized small animal model, which offers an in vivo environment more closely resembling to the situations in human, provides an invaluable and effective approach for in vivo investigating human stem cell behaviors, and further in vivo examining fundamental mechanisms controlling human stem cell fates in the future. The potential for new advances in our better understanding the living biological systems in human provided by investigators in humanized animals will remain promising.

Clinical experience with kidney transplantation in patients older than 65 years

Objective:To explore the peculiarities of kidney transplantation in elderly patients and define the perioperative managements. Methods: The clinical data of kidney transplantation in 29 patients older than 65years were reviewed, the eldest being 84 years old and the mean age 68. 1 years. Results: Four episodes of acute rejection (13. 80%) were encountered. FK506 toxicity occurred in one case (3.40%) and lung infection in another (3.40%), who (along with the former 4 patients) all were cured subsequently. In one case, the kidney graft was removed for thrombogenesis of the renal artery. The 1- and 3-year patients/grafts survival of 100% and 96.5% respectively was achieved, with the longest survival exceeding 5 years. Conclusions:Old age was not the absolute contraindication for kidney transplantation. Strict observance of the indications of kidney transplantation and donor selection with well-matched tissue-typing are crucial in elderly patients.Adequate application of immunosuppressants and effective long-term follow-up are also major factors for long-term allograft survival.

Beneficial effect of an antibody against interleukin-2 receptor (daclizumab) in an experimental model of hepatocyte xenotransplantation

AIM: To investigate the use of Daclizumab (Dmab) as an immunosuppressive agent in an experimental model of hepatocyte xenotransplantation (XenoTx) in rats with fulminant hepatic failure (FHF). METHODS: Two white male New Zealand rabbits were used as donors and 68 Wistar rats as recipients. FHF was induced by intravenous application of dimethylnitrosamine (DMNA). The isolated hepatocytes of the rabbits were xenotransplanted into the spleen of the rats 24 h after FHF induction. Group A (n = 13): no treatment; Group B (n = 14): FHF and XenoTx; Group C (n = 14): FHF and XenoTx and cyclosporin (CsA); Group D (n = 14): FHF and XenoTx and Dmab; Group E (n = 13): FHF and XenoTx and CsA and Dmab. The rats were followed for 15 d. RESULTS: Statistical analysis showed better survival among groups D (92.86%) and E (76.92%) compared to group A (all rats died after 72 h), group B (28.57%) or group C (71.43%), although the differences were not statistically significant. Biochemical evaluation of the liver enzymes and histology confirmed satisfactory function and engraftment, respectively. CONCLUSION: This experimental model has shown the safe, effective and beneficial use of Dmab in a xenotransplantation model of rabbit hepatocytes in rats.

Clinical observation of the effect of tacrolimus (Prograf) against renal allograft rejection in 294 cases

Objective: To study the effect of tacrolimus (Prograf, FK506) in preventing renal allograft rejection. Methods: The curative effect, therapy index, toxicity and side effects of FK506 were observed in 294renal transplant recipients among whom 268 received FK506 24 h after the operation and the other 26 with cyclosporine (CsA) developed acute rejection after transplantation and were given FK506 to replace methylprednisolone (MP) when the latter did not result. All the patients were given oral mycophenolate mofetil (MMF, 1.0 g/d) and meticorten (Pred, 30 mg/d) 24 h later after operation. Results: In the 268 recipients previously mentioned, the incidence of acute rejection was 10. 45%, glycometabolism disorder 9.33%, nervous system disturbance 1.59%, liver function abnormality 2.99%, nephrotoxicity 1.87%, gastrointestinal disorder 17. 5%, cytomegalovirus (CMV) viremia 2.99%, and non-CMV pulmonary infection 1. 59%(4/268), with 1 fatal case for cerebral hemorrhage with normal allograft function and another 2 non-fatal cases in which function loss resulted in removal of the allografts. The blood trough concentrations of FK506were between 5 and 20μg/L. In the 26 cases of steroid-resistant rejection, 23 (88. 46%, 23/26) were reversed and the rest 3 required plasma exchange and application of OKT3 before recovery. Conclusion: As a safe and effective immunosuppressant, FK506 can reduce the incidence of allograft rejection in kidney transplant recipients with little side effects or toxicity, which is particularly applicable in patients with steroid-resistant rejection or CsA nephrotoxicity. Attention should to be paid to glycometabolism disorder due to FK506, however, the long-term effects of FK506 need further investigation.

The Synergistic Effect of HT and Complement Regulatory Proteins in Resisting the Immunological Rejection of Heterogenic Transplantation

Objective：To establish the polytransgenic mice expressing the human HT and complement regulatory proteins （CRPs） and discuss their ability to resist the hyperacute rejection （HAR） and delayed xenograft rejection （DXR） of heterogenic transplantation. Methods ：Transgenic mice were produced by microinjection to construct gene for human HT, delay acceleration factor （DAF） and/or CD59 into the male pronucleus of zygote. PCR and Southern blot were used to screen the positive trarisgenic mice. Flow cytometry （FCM） was used to detect the expression of HT, ct-Gal and DAF or CD59 on the PBMCs of transgenic mice. The survival time and function of the heart of transgenic mice were determined by a modified Langendorff cardiac perfusion apparatus： The change of proteinosis on IgM,IgG, C3c and C9 from different cardiac vascular iendothelial cells of transgenic mice were detected by immunohistochemistry. Results：HT, DAF or CD59 were highly expressed on the positive transgenic mice by FCM. The deposition of IgM,IgG,C3c or C9 in the cardiac vascular endothelial cells of the positive transgenic mice were de- creased. The survival time and function of the heart of the co-transgenic mice with AB serum perfusion were significantly longer and higher than that of the single HT positive transgenic mice（P 〈0.05）. Conclusion ：The mice co-expressing HT/DAF or HT/CD59 could resist the HAR,which was better than those expressing HT alone. It is feasible to use HT and CRPs co-transgenic methods to resist the HAR and DXR.

Influence of mycophenolate mofetil (MMF) upon thematuration and allo-stimulatory activity of cultured progenitors of dendritic cells and the effectson the tolerance induction in allograft recipients

To investigate the influence of mycophenolate mofetil (MMF) upon the maturation and the allo-stimulatory activity of cultured progenitors of dendritic cells (DCp), and to evaluate the effects of the pre-treated dentritic cells of recipients with MMF on the tolerance induction as well as its possible mechanism, GM-CSF and MMF were added to the in vitro cultured progenitor cells, and the immuno-phenotypical analysis was performed by means of flow cytometry. The secretion of IL-12 was detected by ELISA and the stimulatory activities of DCp on allogeneic T cells were observed by mixed lymphocyte reaction. Twenty-four C57BL/6 mice were divided into 3 groups (each with 8 mice), in which group A of mice accepted allografts of heart from BALB/c mice, group B of mice had received untreated DCp from donors of BALB/c mice 7 days before transplantation, and C57BL/6 mice in group C were treated by injection with MMF-treated allografts of heart from BALB/c mice 7 days before transplantation. The survival times of allografts and the changes of the cytokine levels in sera of the recipient mice were observed after transplantation. The experimental results showed that MMF could significantly inhibit the expressions of the co-stimulatory molecules CD80 and CD86 on DCs and the secretion of IL-12 and the allo-stimulatory activities of DCs were also markedly inhibited. The survival times of allografts in group B of mice were longer than those in group A, while the group C showed the longest survival times of allografts, with a marked reduction in the production of the Th1 type cytokines. It is evident that MMF has a suppressive effect on the maturation and allo-stimulatory activities of the cultured dendritic cell progenitors, thus leading to a donor specific tolerance in heart-transplanted recipients.

Developmental Fate of Artificially Disordered Somite Cells after Heteroplastic Transplantation

A disordered somite pattern could be produced artificially when the segmental lateral plate of chick embryo was replaced by dissociated cells of quail segmental pate.The artificially disordered somite pattern formed at either place was used in our work as a model to analyze the mechanism of the development and differentiation of somite on chick embryo. Our conclusions include the following: 1.Although the formation of somites from the dissociated segmental plate cells does not require special environment,the development and differentiation of the somltes require a special environment which is related to the neural tube and notochord.The effect of this special environmental factor may decrease gradually with the increase of the distance from neural tube to lateral plate. 2.The somites located on paraxial area at different distances to the axis have different fates in development. 3.The formation of epithelial vesicles is the property of somite cells and the epithelial vesicle is the structural basis of somite differentiation.If and factor interferes with the differentiation of the somite,the epithelial vesicle of the somite will be degenerated within certain period of time. 4.During resegmentation of the somite,the number,size and arrangement of sclerotome in situ do not depend on the somite from which they are derived. 5.Somite cells do not transdifferentiate into kidney tubule directly from their original epithelial vesicles,but are reorganized from the free cells dispersed from the disrupted somites. 6.The establishment of cell commitment may involve several steps.Before commitment is established the of cell commitment is labile. 7.The differentiation of sclerotome starts with the rupture of epithelial wall of somites and the direction of its movement depends not only on the notochord but also on their position with respect to the neural tube and notochord. 8.The disordered somite pattern doesn't influence the segmentation of dorsal root ganglia in situ, but causes the formation of the ectopic dorsal root ganglia.

The precursor frequency of alloreactive CTLs is proportional to the number of T cell epitope specificities

The aim of this study is to find the experimental evidence that the precursor frequency of alloreactive CTLs is proportional to the number of the T-cell epitope specificities. The number of T-cell epitope specificities was manipulated by pulsing different humor of HLA-A2 restricted peptide（s） onto the T2 cells, which acted as stimulating cells to elicit allo-reaction by co-culturing with peripheral blood lymphocytes （PBLs） of HLA-A2 negative individual. Ten HLA-A2 restricted peptides （all were normal cell components ） were synthesized, and cell peptide extract was prepared by frozen and thawed. T2 cells loaded with different number of peptide（s） were co-cultured with PBLs of an HLA-A2 negative individual; the latter were stained with PKH67 in advance. Then the proliferation was monitored with flow cytometry, and the precursor frequency of the effector cells was ＇analyzed by the ModFit Software. After 6 d of culture, no proliferation was observed in the bulk culture of PBL alone, and obvious proliferation took place when PBLs of the HLA-A2 negative were co-cultured with T2 cells loaded with or without loading peptide（ s）. The precursor frequency of the alloreactive CTLs was 0.052 819 for co-culture with T2 cells loaded without peptide; however it was 0. 030 429 for T2 cells with EBV/LMP2A and 0. 030 528 for T2 cells loaded with a single autogeneic peptide, and increased up to 0. 144 942 for T2 cells loaded with 10 autogeneic peptides; the precursor frequency was 0. 203 649 when co-cultured with T2 cells loaded with miscellaneous peptides extracted from the cytoplasm of T2 cells. This study reveals that the precursor frequency of alloreactive CTLs is proportional to the number of T-cell epitope specificities, and independent of the density of the allogeneic HLA Class Ⅰ molecule. Our findings support the hypothesis that the alloreactive T cell populations comprise miscellaneous T cell clones; each is specific to corresponding pMHC. The novel constellation of peptides presented by allogeneic MHC molecules makes thousands of different epitopes, which account for the exceptional high precursor frequency of alloreactive T cells.