Islet transplantation-immunological challenges and current perspectives

Pancreatic islet transplantation is a minimally invasive procedure aiming to reverse the effects of insulin deficiency in patients with type 1 diabetes(T1D)by transplanting pancreatic beta cells.Overall,pancreatic islet transplantation has improved to a great extent,and cellular replacement will likely become the mainstay treatment.We review pancreatic islet transplantation as a treatment for T1D and the immunological challenges faced.Published data demonstrated that the time for islet cell transfusion varied between 2 and 10 h.Approximately 54%of the patients gained insulin independence at the end of the first year,while only 20%remained insulin-free at the end of the second year.Eventually,most transplanted patients return to using some form of exogenous insulin within a few years after the transplantation,which imposed the need to improve immunological factors before transplantation.We also discuss the immunosuppressive regimens,apoptotic donor lymphocytes,anti-TIM-1 antibodies,mixed chimerism-based tolerance induction,induction of antigen-specific tolerance utilizing ethylene carbodiimide-fixed splenocytes,pretransplant infusions of donor apoptotic cells,B cell depletion,preconditioning of isolated islets,inducing local immunotolerance,cell encapsulation and immunoisolation,using of biomaterials,immunomodulatory cells,etc.

Islet transplantation for diabetic rats through the spleen

BACKGROUND: Islet transplantation is considered a po- tentially curative treatment for diabetic mellitus. The aim of this study was to assess the feasibility of islet transplant through the spleen. METHODS: Both donor and recipient Wistar rats (BW150± 20 g) were provided by the Animal Center of China Medi- cal University, Shenyang, China. Islets were isolated and purified with the modified Minnesota program. 600-800IE graft islets were handpicked and transplanted through the spleen of diabetic recipients. Blood glucose and insulin were evaluated after operation every other day. IVGTT was performed 10 days after transplantation. RESULTS: 300-400IE islet was procured from one donor rat. Secretion index (SI) of the glucose stress was 5.59± 0.62, showing the graft functioning well. The diabetic rats restored normal blood glucose levels of 3.4-5.4 mmol/L (mean 4.8 mmol/L). Their insulin levels were as normal as 8.5-12.2 μIU/ml. The K value of IVGTT in the rats after transplantation was similar to the normal one. CONCLUSIONS: The islets can be transplanted successfully through the spleen, while avoiding the complications caused by traditional transplantation through the portal vein, such as bleeding and portal vein hypertension. The graft islets loss can be reduced because of less centrifugation and mechanic pressure. In conclusion, transplantation through the spleen is a simple and feasible method.

Protective effect of glucocorticoid-free immunosuppressive regimen in allogenic islet transplantation

BACKGROUND: The most common complication after allogenic islet transplantation is rejection. This study was to evaluate the effect of anti-rejection of glucocorticoid-free immunosuppressive regimen on allogenic islet transplantation. METHODS: Tacrolimus(FK506)+mycophenolate mofetil (MMF) and FK506+MMF+prednisone (Pred) were administered respectively for 2 weeks to inhibit rejection after allogenic islet transplantation in rats, which were compared with the control group. The concentrations of blood glucose, insulin and C-peptide were determined dynamically in recipients and the sites of transplantation were observed morphologically. RESULTS: As compared with the control group without immunosuppressive agents, FK506+MMF and FK506+MMF+Pred could prolong the survival time of grafts significantly. There were many morphologically intact islets in the liver of recipients 2 months after transplantation. Group FK506+MMF kept normal levels of blood glucose, insulin and C-peptide beyond 60 days after transplantation. In contrast, group FK506+MMF+Pred secreted less C-peptide(P<0.05) and maintained a higher level of blood glucose concentration (P<0.01) after the operation. There was no significant difference in insulin concentrations between the two groups. The level of blood glucose beyond the first 2 weeks after drug withdrawal in group FK506+MMF+Pred decreased obviously (P<0.05), and the secretion of insulin and C-peptide increased. These results were compared with those the first 2 weeks after transplantation and the first 2 weeks after drug withdrawal. CONCLUSIONS: Both regimens of FK506+MMF and FK506+MMF+Pred could provide effective immunosup-pression. Moreover the combined glucocorticoid-free immunosuppressive strategy of low-dose FK506 and MMF could protect islet grafts in islet transplantation without diabetogenic side-effects.

The establishment of pancreatic islet isolation in India-an update on human pancreatic islet transplantation

Background:Diabetes is a widespread disease with increasing prevalence.Transplantation of islets of Langerhans is a viable treatment for a selected group of patients with repeated hypoglycemic episodes in type 1 diabetes.The countries where islet transplantation has not been explored suffer from insufficient knowledge concerning key elements of the isolation process.Donor and organ procurement parameters impact human islet yield,although for research purposes,islet yield may be secondary in importance to islet function.This paper will analyze the feasibility of research-only human islet isolation and signify parameters underlying a successful yield in the Indian population.This eventually can make islet transplantation a clinical reality in India.Method:After receiving the consent for procuring brain-dead pancreas from the first-degree of relatives,samples were collected and transported in a transportation buffer at 4℃.The procedure consists of a mechanically enhanced enzymatic digestion of the pancreas,after which it was taken for purification using Ficoll method,followed by islet quality testing.Results:Through 15 isolations done over a span of approximately 2 years during the COVID pandemic in India,we confirm that ischemic time and glycated hemoglobin,each have a negative impact on isolation purity and yield.Notably,extending cold ischemic tim beyond the typical clinical isolation cutoff of 12 hours(to≥18 h)had a huge impact on islet function and yield.Age had a negative correlation with islet yield;however other biological parameters(specifically body mass index)and isolation variables appear to make a significant contribution to the heterogeneity of human islet yield.Our current work demonstrates the feasibility of extending acceptable cold ischemic time for research-focused human islet isolation and highlights the biological variation in isolation of human islets from donors with and without diabetes.Conclusion:India requires establishment of an islet transplant program using the current standard methods of“islet isolation”and donor program and process.Research should focus on improving standards in the islet preparation process to increase the number of successful preparations,shorten the isolation time,and increase patient safety so that the theoretical risk involved can become a practical reality.

Is islet transplantation ready for widespread use in diabetes？

Up till 2000 when Edmonton group introduced islet transplant procedure in conjunction with a novel glucocorticoid-free immunosuppressive regimen rendering 100% （n=7） of patients with type 1 diabetes insulin-independent for at least 1 year, islet transplant was taken into the clinic. Although significant progress in clinical islet transplant has occurred during recent years, challenges remain, including shortage of available donor organs, technical aspects of islet preparation and transplantation, immunological rejection post-transplant, unclear long-term outcomes of islet transplantation. Special attention is given to current limitation in islet transplantation together with new possible strategies that raise expectations for the widespread use of islet transplantation in the future.

Induction of islet transplantation tolerance with anti-CD_4, anti-CD_8 immunotoxins and donor soluble antigen

Objective To induce islet grafting tolerance by intravenous injection of anti CD 4, anti CD 8 immunotoxins and donor soluble antigen Methods Fourteen days or 7 days prior to transplantation, the immunotoxin of anti CD 4, anti CD 8 200?μg respectively, and donor soluble antigen 500?μg were intravenously injected and then 500 donor islets were transplanted under the left renal subcapsular space of diabetes recipients (Sprague Dawley rats) Results The islet grafting survival time for those recipients pretreated with immunotoxin and donor soluble antigen was >60 days ( P <0 01) The immunotoxins, donor soluble antigen treatment alone might only slightly prolong the grafting survival time Conclusion The anti CD 4, anti CD 8 immunotoxins jointly used with donor soluble antigen can induce donor specific immunotolerance

Monitoring of clinical islet transplantation

Islet transplantation has recently emerged as one of the most promising therapeutic approaches to improving glycometabolic control in diabetic patients. The Edmonton trials demonstrated a marked improvement in the short-term rate of success of islet transplantation, with an 80% rate of insulin-independence being at 1 year after transplantation, as reported by several institutions worldwide. Unfortunately, this rate consistently decreases to 10% by 5 years post-transplantation.

Two-layer cold storage method for pancreas and islet cell transplantation

The two-layer cold storage method (TLM) was f irst reported in 1988, consisting of a perfluorochemical (PFC) and initially Euro-Collins' solution, which was later replaced by University of Wisconsin solution (UW). PFC is a biologically inert liquid and acts as an oxygen-supplying agent. A pancreas preserved using the TLM is oxygenated through the PFC and substrates are supplied by the UW solution. This allows the pancreas preserved using the TLM to generate adenosine triphosphate during storage, prolonging the preservation time. In a canine model, the TLM was shown to repair and resuscitate warm ischemically damaged pancreata during preservation, improve pancreas graft survival after transplantation, and also improve the islet yield after isolation. Clinical trials using the TLM in pancreas preservation before whole-pancreas transplantation and islet isolation have shown promising outcomes. We describe the role of the TLM in pancreas and islet transplantation.

Alternative therapeutic strategies in diabetes management

Diabetes is a heterogeneous metabolic disease characterized by elevated blood glucose levels resulting from the destruction or malfunction of pancreaticβcells,insulin resistance in peripheral tissues,or both,and results in a non-sufficient production of insulin.To adjust blood glucose levels,diabetic patients need exogenous insulin administration together with medical nutrition therapy and physical activity.With the aim of improving insulin availability in diabetic patients as well as ameliorating diabetes comorbidities,different strategies have been investigated.The first approaches included enhancing endogenousβcell activity or transplanting new islets.The protocol for this kind of intervention has recently been optimized,leading to standardized procedures.It is indicated for diabetic patients with severe hypoglycemia,complicated by impaired hypoglycemia awareness or exacerbated glycemic lability.Transplantation has been associated with improvement in all comorbidities associated with diabetes,quality of life,and survival.However,different trials are ongoing to further improve the beneficial effects of transplantation.Furthermore,to overcome some limitations associated with the availability of islets/pancreas,alternative therapeutic strategies are under evaluation,such as the use of mesenchymal stem cells(MSCs)or induced pluripotent stem cells for transplantation.The cotransplantation of MSCs with islets has been successful,thus providing protection against proinflammatory cytokines and hypoxia through different mechanisms,including exosome release.The use of induced pluripotent stem cells is recent and requires further investigation.The advantages of MSC implantation have also included the improvement of diabetes-related comorbidities,such as wound healing.Despite the number of advantages of the direct injection of MSCs,new strategies involving biomaterials and scaffolds have been developed to improve the efficacy of mesenchymal cell delivery with promising results.In conclusion,this paper offered an overview of new alternative strategies for diabetes management while highlighting some limitations that will need to be overcome by future approaches.

Triptolide prolonged allogeneic islet graft survival in chemically induced and spontaneously diabetic mice without impairment of islet function

BACKGROUND: Triptolide (TPT) is a diterpenoid triepoxide extracted from the Chinese herb Tripterygium wilfordii Hook. F. It exhibits potent immunosuppressive and anti-inflammatory properties. This study was undertaken to investigate its effects on prolongation of islet allograft survival in rodents. Additionally, we investigated whether TPT would be toxic to islet function in vivo. METHODS: We transplanted BALB/c islets to either chemically induced diabetic C57BL/6 mice or spontaneously diabetic non-obese diabetic (NOD) mice. TPT was injected within 2 weeks or continuously, until rejection, in the two combinations. Then, we evaluated the toxicity of TPT on islet function by daily injection to naive BALB/c or diabetic BALB/c that was cured by syngeneic islet transplantation under the kidney capsule. Mice injected with cyclosporine A (CsA) or vehicle served as controls. Intraperitoneal glucose tolerance tests (IPGTTs) performed at 4 and 8 weeks in the naive BALB/c group, and at 2, 4, 6, and 8 weeks in the syngeneic transplanted group. RESULTS: The medium survival time of islets allograft from TPT treated C57BL/6 and NOD recipients were 28.5 days (range 24-30 days, n=10) and 33.0 days (range 15-47 days, n=6), respectively, and they were significantly different from those of the vehicle treated controls, which were 14.0 days (range 13-16 days, n=6) and 5.0 days (range 4-10 days, n=6), respectively (all P<0.0001). The IPGTT demonstrated that there was no difference between the TPT treated and vehicle treated groups, either in the normal or syngeneic transplanted islet BALB/c mice. However, CsA injection impaired islet function in both normal and syngeneic transplanted mice as early as 4 weeks. CONCLUSION: TPT prolonged islets allograft survival in a chemically induced diabetic or an autoimmune diabetic murine model without impairment of islet function. (Hepatobiliary Pancreat Dis Int 2010; 9: 312-318)

Bone marrow cells produce nerve growth factor and promote angiogenesis around transplanted islets

AIM:To clarify the mechanism by which bone marrow cells promote angiogenesis around transplanted islets.METHODS: Streptozotocin induced diabetic BALB/ c mice were transplanted syngeneically under the kidney capsule with the following: (1) 200 islets (islet group: n=12), (2) 1-5×106 bone marrow cells (bone marrow group: n=11), (3) 200 islets and 1-5×106 bone marrow cells (islet + bone marrow group: n= 13), or (4) no cells (sham group:n=5). All mice were evaluated for blood glucose, serum insulin, serum nervegrowth factor (NGF) and glucose tolerance (GTT) up to postoperative day (POD) 14. Histological assessment for insulin, von Willebrand factor (vWF) and NGF was performed at POD 3, 7 and 14.RESULTS: Blood glucose level was lowest and serum insulin was highest in the islet + bone marrow group. Serum NGF increased in islet, bone marrow, and islet + bone marrow groups after transplantation, and there was a significant difference (P=0.0496, ANOVA) between the bone marrow and sham groups. The number of vessels within the graft area was signif icantly increased in both the bone marrow and islet + bone marrow groups at POD 14 as compared to the islet alone group (21.2 ± 3.6 in bone marrow, P=0.01, vs islet group, 22.6 ± 1.9 in islet + bone marrow, P = 0.0003, vs islet group, 5.3 ± 1.6 in islet-alone transplants). NGF was more strongly expressed in bone marrow cells compared with islets. CONCLUSION: Bone marrow cells produce NGF and promote angiogenesis. Islet co-transplantation with bone marrow is associated with improvement of islet graft function.

The effect of FasL gene transfer to islet cells on pancreatic islet allografts

OBJECTIVE: To investigate the effect of FasL gene transfer to islet cells on pancreatic islet allografts. METHODS: A recombinant and replication-deficient type-5 adenovirus encoding murine FasL (AdV- FasL) was constructed by the method of calcium phosphate precipitation. Pancreatic islets were infected with the recombinant adenovirus AdV-FasL, and transplanted into diabetic recipients. FasL expression was detected by RT-PCR and immunohistochemistry. The survival of allografts and the apoptosis of gene transferred islet allografts were analyzed. RESULTS: All animals receiving islet allograft alone returned to a diabetic state by several days (mean survival time 6.3±0.6 days). Compared with the control group, no delayed rejection and prolonged survival of allografts were observed in the group of FasL gene transfer. The rejection was accelerated and the allograft survival was shortened to 3.4±0.2 days (P<0.05). Pancreatic islets infected with AdV- FasL demonstrated positive staining of FasL at 24 h, with an increased intensity at 48 h, but not in AdV-5 infected or uninfected islets. TUNEL labeling of pancreatic islet allografts at 24, 48 h revealed apoptosis that was not in AdV-5 infected allografts. CONCLUSIONS: Though co-transplantation of FasL-expressing testicular cells can induce privilege of islet allografts and prolong allograft survival, direct expression of FasL on islet allografts infected with AdV-FasL may accelerate islets rejection by islet apoptosis and granulocyte infiltration.

Role of OX40 in mechanisms of memory T cells in islet transplant tolerance

Objective To investigate the role of OX40 in the mechanisms of memory T cells in islet transplant tolerance. Methods The expression of OX40 on native, like memory and memory CD8 + T cells was detected by RT - PCR. Splenic T ceels from B6 mice were injected into Rag - / - mice via the tail vein,and the Rag mice were divided into three groups ( n = 8 each) :

A case of abdominal abscess after simultaneous omentum intraomental bio-scaffold islet-kidney transplantation

Compared with patients who undergo renal and islet transplantation sequentially,simultaneous omentum intraomental bio-scaf-fold islet-kidney transplantation in patients with type 1 diabetes complicated by renal failure has the advantages of donor homolo-gation,less trauma,lower cost,and easier acceptance by patients.Omentum intraomental bio-scaffold islet has been gradually applied in clinical practice,and rare clinical complications have been reported.Here we report a case of abdominal abscess associated with extended-spectrum β-lactamase in a patient who underwent simultaneous omentum intraomental bio-scaffold islet-kidney transplantation;the islet grafts remained partially functional after appropriate anti-infective treatment.

Application of anti-CD103 immunotoxin for saving islet allograft in context of transplantation

Background Previous studies using knockout mice document a key role for the integrin CD103 in promoting organ allograft rejection and graft-versus-host disease. However, a determination of whether blockade of the CD103 pathway represents a viable therapeutic strategy for intervention in these processes has proven problematic due to the lack of reagents that efficiently deplete CD103＋ cells from wild type hosts. To circumvent this problem, in the present study, we invented an anti-CD103 immunotoxin （M290-SAP）. We investigated whether M290-SAP has capacity to eliminate CD103-expressing cells in vivo and protect transplanted islets from destroying by host immune cells.Methods Flow cytometry was used to analyze the efficacy of M290-SAP in depleting CD103-expressing cells in vivo.Then using allogenic islet transplantation models as well as NOD mice with recent onset type 1 diabetes, the therapeutic efficacy of CD103-expressing cell depletion was addressed.Results M290-SAP dramatically reduces the frequency and absolute numbers of CD103-expressing leukocytes in peripheral lymphatic tissues of treated mice. Balb/c islets transplanted into streptozotocin-induced diabetic C57BL/6 mice under single M290-SAP treatment showed an indefinite survival time compared with untreated mice, M290-treated mice and IgG-SAP treated mice （mean survival time, ＞100 days vs. ＜20 days）. C57BL/6 islets transplanted into hyperglycemic NOD mice under single M290-SAP treatment showed a pronounced delay in allograft rejection compared with untreated mice （mean survival time 12-13 days vs. ＜7 days）. Immunological analysis of mice with long-term islet allograft survival revealed an obvious atrophy thymus and severe downregulation of alloimmunity of CD8 subpopulation response to allogenic stimulation.Conclusion Regardless of the underlying mechanisms, these data document that depletion of CD103-expressing cells represents a viable strategy for therapeutic intervention in islet allograft rejection.

Isolation and culture of adult Sertoli cells and their effects on the function of co-cultured allogeneic islets in vitro

Background Globally, 180 million people suffer from diabetes mellitus. Islet transplantation is believed to be an almost ideal therapy for insulin-dependent patients. How to maintain the viability and the function of isolated human islets is a challenge in clinical practice. Sertoli cells are considered ＇ nurse cells＇ in the seminiferous tubules and have been used in cell graft protocols for neurodegenerative diseases and diabetes in many studies. Many researchers have used immature murine testes as the primarily source of Sertoli cells in islet transplantation because they are easily purified. Mature human Sertoli cells have been seldom investigated. In the present study, we developed a method for the isolation and culture of Sertoli cells derived from adult human testes, and investigated their effects on the function of allogeneic islets when they were cultured together in vitro. Methods Adult Sertoli cells were prepared successfully by two-step enzyme digestion with trypsin, collagenase and hyaluronidase. They were identified by morphological characteristics and their activity was determined by MTT colorimetry over a 28-day culture time in vitro. A glucose-stimulated insulin secretion test was performed to detect the effects of Sertoli cells on allogeneic islets＇ function when they were co-cultured for 21 days in vitro. Results In cultured cells, mature human Sertoli cells accounted for more than 90% of total cells. The activity of Sertoli cells reached 95 % and they remained highly cytoactive for a long time in vitro （P〉0. 05 ）. Compared with the islets cultured alone, the co-cultured islets with allogeneic Sertoli cells maintained higher sensitivity to glucose stimulation for the duration of the experiment （P〈0.01 ）. Conclusions A method of isolation and culture of Sertoli cells from adult testes has been established. Sertoli cells could enhance allogeneic islets＇ function when they were co-cultured in vitro. They could be a helper cell in islet transplantation.

Hemo oxygenase-1 induction in vitro and in vivo can yield pancreas islet xenograft survival and improve islet function

Background The induced expression of heme oxygenase-1 （HO-1） in donor islets improves allograft survival. Cobalt protoporphyrin （CoPP） could significantly enhance the expression of HO-1 mRNA and protein in rat islet safely. Our work was to study how to protect pancreatic islet xenograft by CoPP-induction. Methods Islet xenografts treated with CoPP-induction and CoPP＋ Zinc protoporphyrin （ZnPP） in vitro and in vivo were randomly transplanted into murine subrenal capsule; then the graft survival time was compared by blood glucose level and pathological examination and meanwhile the interferon ~ （IFN-y）, tumor necrosis factor a （TNF-a）, interleukin 10 （IL-10） and IL-113 level in serum and their mRNA and HO-1 mRNA and protein expression were examined. Results Islets with CoPP-induction under low- and high-glucose stimulation exhibited much higher insulin secretion compared with other three groups. CoPP-induction could increase higher expression of HO-1 （mRNA： 3.33- and 76.09- fold in vitro and in vivo; protein： 2.85- and 58.72-fold）. The normoglycemia time in induction groups （（14.63±1.19） and （16.88±1.64） days） was significantly longer. The pathological examination showed less lymphocyte infiltration in induction groups. The IL-10 level and its mRNA in induction groups were significantly higher. Conclusions The HO-1 induced by CoPP would significantly improve function, prolong normoglycemia time and reduce lymphocyte infiltration. Meanwhile CoPP-induction in vivo had more beneficial effects than in vitro. Its mechanism could be related to immune-modulation of IL-10.

Investigation of long-term preservation of pancreatic islets

Objective To develop a method for maintaining viability and function of islets of Langerhans during the long term preservation.Methods We encapsulated Wistar Furth (WF) rat islets in hydrophilic macrobeads (diameter 6-8 mm) made with agarose and collagen, then preserved them at 37℃ in a humidified atmosphere of air and 5% CO 2 for different time, and compared unencapsulated islets with encapsulated islets for their insulin secretion capability in vitro. At the same time, we have investigated their viability and insulin secreting function in vivo.Results Initially, there was no statistically significant difference in the insulin secretion values between the encapsulated and unencapsulated WF rat islets. While the unencapsulated islet insulin secretion decreased significantly within 2 weeks, the preserved and encapsulated islets maintained their viability and ability of insulin secretion for 40 weeks. In the in vivo study, the diabetic state was reversed in 92.8% of recipients transplanted with preserved macroencapsulated islets. The mice maintained normoglycemia for 157.6±49.3 days, at which point these macrobeads were retrieved. Glucose tolerance curves in the recipient mice were similar to those of normal mice. Conclusions These results indicate that it is a good method for long term preservation of islets by encapsulating islets in agarose and collagen, and then culturing them at 37℃ in a humidified atmosphere of air and 5% CO 2 before transplantation.

IL-10 Gene Modified Dendritic Cells Inhibit T Helper Type 1-Mediated Alloimmune Responses and Promote Immunological Tolerance in Diabetes

Dendritic cells （DCs） have the potency to regulate the outcome of autoimmunity through the modulation of immune responses. The induction of antigen specific tolerance is critical for prevention and treatment of allograft rejection. In the present Study, we transfected IL-10 gene into DCs and investigated their effect on inhibition of lymphocyte activity in vitro and induction of immune tolerance on islet allograft in mice. An IDDM C57BL/6 mouse model was induced by streptozotocin. The islet cells isolated from the BALB/c mice were transplanted into the kidney capules of the model mice followed by injection of IL-10 modified DCs （mDCs）. The results showed that mDCs could significantly inhibit T lymphocyte proliferation mediated by allotype cells and induce its apoptosis, whereas, unmodified DCs （umDCs） could promote the murine lymphocyte proliferation markedly. The injection of mDCs could prolong the survival of allotype islet transplanted IDDM mice. The average plasma glucose （PG） level in mDCs treated mice returned to normal within 3 days and lasted for about 2 weeks. The rejection response in control mice occurred for 5 days after transplantation. The level of IFN-γ was lower while IL-4 was higher in mDCs treated mice than that in umDCs treated mice, which indicated that Thl/Th2 deviation occurred. Our studies suggest that IL-10 gene modified DCs can induce the immune tolerance to islet graft and prolong survival of the recipients by the inhibiting of T cell proliferation in allotype mice. Cellular ＆ Molecular Immunology.

Effects of Tripterygii Totorumin Treat ing Insulin Dependent Diabetes Mellitus Patients with lslet Transpl

The authors determined both the numbers of T Iymphocyte subpopulations in peripheralblood and the concentration of Cpeptide in serum before experimentation at 15 days, 1 month, 6 months,and 1 year atter islet transplantation in tripterygii totorum (T Ⅱ ) group in which 30 insulin dependent dia-betes mellitus (IDDM) patients were given T Ⅱ and the control group in which 24 IDDM patients did notuse any immunosuppressive agents, and 20 healthy individuals were used as the healthy group. Results:Before transplantation, the numbers of T lymphocyte subpopulations such as CD2,CD4 in the two groupswere lower than those in the healthy group (P<0. 01) the ratio of CD4/CD8 was between 1. 2 and 2. 0.Atter transplantation the numbers of CD2, CD4 in the two groups were elevated, particulary in T Ⅱ groupthe numbers of CD2, CD4 were close to those in the healthy group (P>0. 05) . The ratio of CD4/CD8 in thecontrol group was more than 2. 0. The average dose ot insulin reduced by 84. 2% in 19 patients of the T Ⅱgroup, 2 cases stopped insulin, the peak value of C-peptide was 3. 24±1. 2 ng/ml. In the control groupthe average dose of insulin and the peak value of C-peptide was similar to that in the T Ⅱ group in the first6 months atter transplantation (P>0. 05) , then the dose ot insulin was gradually increased and the con-centration of C-peptide began decreasing. One year after transplantation both the dose of insulin and theconcentration of C-peptide were close to those before transplantation. The study suggests that T Ⅱ haveimmunosuppressive effects in islet transplantation and prolong the survival time of gratts in IDDM patients.