Regulatory mechanism of peripheral tolerance: in vitro evidence for dominant suppression of host responses during the maintenance phase of tolerance to renal allografts in miniature swine

BACKGROUND: Studies from our laboratory have demonstrated that a short course of cyclosporine leads to indefinite survival of renal allografts across an MHC class-I barrier in miniature swine. We have recently reported that a peripheral regulatory mechanism appears to be involved in the maintenance of this tolerance since peripheral blood lymphocytes (PBL), exposed to donor antigen in vitro specifically suppressed the generation of anti-donor cytotoxic activity by recipient-matched naive PBL. We have now further investigated the mechanism of this phenomenon to determine the level at which such regulation occurs, and investigated the phenotypes of the cells involved in maintaining dominant suppression. MATERIALS AND METHODS: PBL from long-term tolerant animals (>6 months after renal transplantation) were pre-stimulated in vitro with donor-type PBL. These cells were then incubated with recipient-matched naive responders and donor-type PBL stimulators in MLR assays. The proliferative activity of the cells was measured by [3H]-thymidine incorporation. Suppression was measured by inhibition of proliferation of naive cells in response to donor PBL when co-cultured with tolerant cells. Flow cytometry was used to study the phenotypes of cells that were present in cell cultures. RESULTS: Primed PBL from tolerant animals markedly suppressed the proliferative response of recipient-matched naive cells to donor-matched stimulators in vitro. No suppression of proliferation was observed in response to third party stimulators, indicating that the suppression was donor-specific. Primed PBL from naive animals stimulated with donor antigen and co-cultured with unprimed recipient-matched naive cells also demonstrated reduced proliferative responses. However, this decrease in proliferation appeared to be due to a 'burn-out' phenomenon, as assessed by kinetic studies, rather than due to true suppression. Expression of CD25 increased on a sub-population of T cells from tolerant animals following priming with donor antigen. These cell then markedly inhibited further activation of CD25 positive cells in co-cultures with naive responder cells, suggesting a possible mechanism of suppression. CONCLUSION: These results suggest that the mechanism of tolerance to class-I-mismatched renal allografts, involves a population of regulatory cells that are capable of suppressing proliferative anti-donor responses.     

Alemtuzumab induction and belatacept maintenance in marginal pathology renal allografts

We performed a prospective, 12‐month, single‐center, nonrandomized, open‐label pilot study to investigate the use of belatacept therapy combined with alemtuzumab induction in renal allografts with preexisting pathology, as these kidneys may be more susceptible to additional toxicity when exposed to calcineurin inhibitors posttransplant. Nineteen belatacept recipients were matched retrospectively to a cohort of tacrolimus recipients on the basis of preimplantation pathology. The estimated glomerular filtration rate was not significantly different between belatacept and tacrolimus recipients at either 3 or 12 months posttransplant (59 vs 45, P = 0.1 and 56 vs 48 mL/min/1.72/m², P = 0.3). Biopsy‐proven acute rejection rates at 12 months were 26% in belatacept recipients and 16% in tacrolimus recipients (P = 0.7). Graft survival at 1 year was 89% in both groups. Alemtuzumab induction combined with either calcineurin inhibitor or costimulatory blockade therapies resulted in similar acceptable one‐year outcomes in kidneys with preexisting pathologic changes. Longer‐term follow‐up may be necessary to identify preferential strategies to improve outcomes of kidneys at a higher risk for poor function (ClinicalTrials.gov—NCT01496417).     

抑制性T淋巴细胞在大鼠同种心脏移植免疫耐受中的作用

目的　探讨抑制性T淋巴细胞在同种心脏移植免疫耐受中的作用。方法　将纯系DA(供体 )、纯系Lewis大鼠 (受体 )各 5 0只随机分为未处理组、脾细胞组、环磷酰胺组、脾细胞 环磷酰胺组、转移组 ,每组受、供体鼠各 10只 ,各组受体鼠分别采用不处理、门静脉注入供体脾细胞 ( 3× 10 8个 )、腹腔注入环磷酰胺 ( 80mg/kg)、供体脾细胞 环磷酰胺、脾细胞 环磷酰胺组心脏移植术后30d受体大鼠脾细胞进行免疫耐受诱导后行腹部心脏移植 ;观察各组供心存活时间、病理改变及供受体间的混合淋巴细胞反应 (MLR)。结果　脾细胞 环磷酰胺组产生了长期的免疫耐受 ,供心平均存活时间为 ( 71 5± 2 9 1)d ,较未处理组、脾细胞组、环磷酰胺组均显著延长 (t=- 14 0 6 3,- 13 915 ,- 13 777,均P <0 0 1) ,供心仅有少量炎性细胞浸润 ,供受体间MLR特异性降低 (t =2 9 90 2 ,P <0 0 1)。转移组供心平均存活时间为 ( 5 2 3± 7 5 )d ,供心仅有少量炎性细胞浸润 ,供受体间MLR特异性降低 (t=2 3 0 4 7,P <0 0 1)。结论　脾细胞 环磷酰胺可成功诱导同种大鼠心脏移植的免疫耐受 ,其免疫耐受状态可过继转移给正常的同系受体 ,抑制性T淋巴细胞在这种免疫耐受状态中起重要作用     

Role of the thymus in transplantation tolerance in miniature swine: II. Effect of steroids and age on the induction of tolerance to class I mismatched renal allografts

BACKGROUND: Recent studies in young (5-7 months) miniature swine have demonstrated that the thymus is involved in the rapid induction of stable tolerance to class I mismatched renal allografts after a 12-day course of Cyclosporine (CyA). Because both steroids and age are known to influence the structure and function of the thymus, we have now studied the effects of these two parameters on tolerance induction in this model. MATERIALS AND METHODS: In young swine, the administration of methylprednisolone (MP) during the standard tolerance-inducing regimen (a 12-day course of CyA) produced severe renal dysfunction and acute cellular rejection histologically. However, the renal allografts recovered and were accepted for >100 days with histological evidence of chronic rejection. To test the effect of age, two relatively old swine (55 and 71 months) received transplants of class I mismatched renal allografts and the standard 12-day course of CyA. One animal rejected the allograft acutely on postoperative day 22, and the second also rejected, but more slowly, with manifestations of chronic rejection. CONCLUSION: These findings suggest that both MP and old age interfere with the induction of stable tolerance in a fashion similar to the previously described effect of thymectomy. These results may have important implications for the mechanism of thymic-dependent tolerance, for the use of steroids in clinical protocols for the induction of allograft tolerance, and for the application of such protocols to adult patients.     

Role of the thymus in transplantation tolerance in miniature swine. III. Surgical manipulation of the thymus interferes with stable induction of tolerance to class I-mismatched renal allografts

BACKGROUND: Previous studies have demonstrated that long-term tolerance of class I mismatched renal allografts in miniature swine is induced by a short course of cyclosporine (CyA), and that a total thymectomy 21 days before transplantation abrogates the induction of stable tolerance. We have now examined the effects of surgical manipulation of the thymus, with or without a reduction in the thymic volume, on the induction of tolerance. MATERIALS AND METHODS: Miniature swine receiving a transplant of a class I-mismatched renal allograft and 12 days of CyA underwent either (1) a partial thymectomy 21 days before kidney transplantation (day -21), (2) serial thymic biopsies (to evaluate the effect of surgical trauma and reduction in volume of the thymus) or serial incisions of the thymus thymus (to evaluate the effect of surgical trauma without changes in thymic volume), (3) a sham thymectomy on day -21, or serial sham thymic surgery on the same POD as the thymic biopsies and incisions (control animals). RESULTS: Control animals had a stable plasma creatinine, had donor-specific unresponsiveness in cell-mediated lympholysis (CML) assays, had absence of rejection in kidney biopsy specimens, and did not develop anti-donor class I immunoglobulin (Ig)G alloantibodies. Animals undergoing a partial thymectomy on day -21 or serial thymic biopsies showed severe renal dysfunction, histological evidence of rejection in kidney biopsy specimens and anti-donor reactivity in CML assays; all but one animal developed anti-donor class I IgG alloantibodies. Serial incisions of the thymus induced an increase in plasma creatinine and histological rejection in 1 of 3 animals and anti-donor cytotoxic T cells in vitro in all 3 animals. CONCLUSIONS: A partial thymectomy or serial thymic biopsies markedly interfere with the induction of tolerance to renal allografts. Serial thymic incisions also interfere with the induction of tolerance, but to a lesser degree. These studies may have implications for tolerance-inducing protocols that involve thymic manipulation.     

Optimizing tacrolimus therapy in the maintenance of renal allografts: 12-month results

BACKGROUND: The determination of optimal tacrolimus (TAC) trough levels is needed to prevent adverse effects of calcineurin inhibitors. METHODS: Stable transplant recipients currently receiving cyclosporine (CsA) were assigned randomly (1:1:1) to continue CsA (target trough level of 50-250 ng/mL); or convert to "reduced" TAC (target trough level 3.0-5.9 ng/mL) or "standard" TAC (target trough level 6.0-8.9 ng/mL). RESULTS: At 12 months, there was a significant improvement in renal function in the reduced TAC versus CsA group with lower serum creatinine (P=0.004) and cystatin C (P<0.001), and higher estimated creatinine clearance (P=0.017). However, there were no statistically significant differences in any renal parameter in the standard TAC versus CsA group. Total and low-density lipoprotein cholesterol were significantly reduced in both TAC groups versus the CsA group (P<0.001). Patient and graft survival and episodes of biopsy-confirmed acute rejection were similar for all treatment groups, and no statistically significant differences were observed between groups in the incidence of new-onset diabetes or cardiac conditions, or in the prevalence of hyperglycemia, hypertension, or hyperlipidemia among patients who did not have these conditions at baseline. Alopecia developed more commonly among TAC-treated patients than CsA-treated patients (P<0.001). CONCLUSIONS: Compared with CsA continuation, conversion to reduced TAC target trough concentrations resulted in significantly improved renal function without increasing the risk of rejection. Conversion to TAC, regardless of target concentration, resulted in improved serum lipid profiles in kidney transplant recipients at 12 months.     

Acceptance reaction: intragraft events associated with tolerance to renal allografts in miniature swine

Inbred miniature swine that are treated for 12 d with a high dose of cyclosporin A develop tolerance to MHC class II matched, class I-mismatched renal allografts. The aim of this study was to clarify the intrarenal allograft events associated with the development of tolerance in this protocol. Morphologic and immunologic studies were performed in serial biopsies from accepting grafts after 12 d of cyclosporin A treatment (n = 4) and were compared with those from untreated control rejecting grafts (n = 4). In accepting grafts with stable function, a transient interstitial infiltrate developed. The cellular infiltrate had many similarities to that in rejecting grafts; both had T cells and macrophages, similar proportions of T-cell subsets, and a similar frequency of in situ nick end labeling (TUNEL)+ apoptotic infiltrating cells. However, the cellular infiltrate in the acceptance reaction was distinguished by less T-cell activation (interleukin-2 receptor+), less proliferation (proliferating cell nuclear antigen+) of infiltrating cells, and less graft cell apoptosis in arteries, tubules, glomeruli, and peritubular capillaries. Thereafter, the infiltrate in the accepting grafts progressively resolved with decreased cell proliferation, activation, and apoptotic graft parenchymal cell injury, but the high frequency of apoptosis persisted in graft-infiltrating cells. In parallel to the intragraft events, donor-specific unresponsiveness developed as assessed by cell-mediated cytotoxicity by blood mononuclear cells in vitro. In conclusion, the acceptance reaction in transplanted grafts is characterized by progressive resolution of T-cell proliferation and activation and of cell-mediated graft injury, as well as prolonged T-cell apoptosis. These intragraft events suggest that both T-cell anergy and T-cell deletion occur in the graft during the development of tolerance. Some of the described immunopathologic findings (activation, proliferation, apoptosis) may be useful in distinguishing acceptance from rejection, as well as in predicting later graft acceptance in tolerance induction protocols.     

新型HLA衍生肽延长异基因大鼠移植肾存活时间

目的观察一种新型的人类白细胞抗原衍生肽(RDP1258)对大鼠肾移植后的免疫抑制作用。方法采用标准Fmoc法人工合成RDP1258。建立异基因大鼠原位肾移植模型。将已建立肾移植模型的大鼠随机分为4组,每组8只。A组:使用RDP1258 环孢素A(CsA);B组:单独使用RDP1258;C组:单独使用CsA;D组:不用任何药物。观察各组大鼠的存活时间,监测血清肌酐浓度,并进行移植肾彩色多普勒超声和常规病理检查。采用体外混合淋巴细胞反应(MLR)法检测长期存活大鼠的供者特异性免疫耐受状态。结果A、B、C和D组平均存活时间分别为(63.4±30.6)d、(18.3±7.3)d、(16.9±6.4)d和(9.4±2.6)d。A组与其他3组比较,差异有统计学意义。另外,混合淋巴细胞培养结果提示,长期存活的受者脾细胞对供者脾细胞的刺激不表现出明显细胞增殖反应,而对无关大鼠脾细胞仍能产生较明显的增殖反应。结论肾移植术后应用RDP1258结合小剂量CsA,能显著延长异基因大鼠移植肾存活时间,其机制可能与RDP1258诱导了受者对供者的特异性移植免疫耐受有关。     

Induction of specific tolerance to class I-disparate renal allografts in miniature swine with cyclosporine.

Previous studies in miniature swine have suggested that the mechanism underlying the spontaneous development of tolerance in one third of one-haplotype class I disparate renal allografts (i.e., ag----ad) involves a relative T cell help deficit at the time of first exposure to antigen. If this hypothesis were correct, then one might expect the administration of an immunosuppressive agent capable of inhibiting lymphokine production during this period to lead to the induction of tolerance to class I MHC antigens in two-haplotype class I mismatched renal allografts (i.e., gg----dd), which are otherwise uniformly and acutely rejected. This hypothesis was tested in eight two-haplotype class I disparate, class II matched donor-recipient pairs, in which recipients were treated with cyclosporine 10 mg/kg, i.v. q.d. for 12 days. This protocol led to the induction of long-term (greater than 100 days) specific tolerance in 100% of recipients, as compared with control animals that rejected grafts in 13.7 +/- 0.9 days (P less than 0.0001). The specificity of tolerance was assessed both in vivo with subsequent skin grafts and in vitro by mixed lymphocyte response (MLR) and cell-mediated lymphocytotoxicity (CML). Survival of donor-specific skin grafts was prolonged compared with skin grafts bearing third-party class I antigens (19.5 +/- 2.0 versus 11.5 +/- 2.0 days, n = 4, P less than 0.05). Tolerant recipients had markedly diminished or absent anti-donor MLR and CML responses, but maintained normal reactivity to third party. Four of eight CsA-treated recipients showed detectable levels of anti-donor IgM, while none demonstrated the presence of anti-donor IgG, which was found in all rejecting controls.     

Successful induction of long-term specific tolerance to fully allogeneic renal allografts in miniature swine.

Major histocompatibility complex class II matching is of overwhelming importance for achieving tolerance to kidney transplants (KTX) in miniature swine. When class II antigens are matched, long-term specific tolerance across complete MHC class I antigen barriers can uniformly be induced by a 12-day perioperative course of cyclosporine. This same regimen is ineffective in fully MHC-mismatched combinations. We hypothesized that initial induction of tolerance to kidney donor class II antigens by bone marrow transplantation might allow tolerance to be induced to a subsequent fully allogeneic KTX in combination with CsA therapy. We report here the results of such fully allogeneic KTX performed in 4 recipients of prior single-haplotype class II-mismatched BMT. All animals received KTX from donors class II matched to the BMT donor and received a 12-day course of intravenous CsA (10 mg/kg/day). All four animals have maintained normal serum creatinine values (less than 2.0 mg/dl) for greater than 200 days posttransplant. Specific hyporesponsiveness to both BMT and KTX donor-type MHC antigens was found in mixed lymphocyte culture and cell-mediated lympholysis assays. Compared with third-party grafts, significantly prolonged survival of BMT donor-specific (P = 0.031) and KTX donor-specific (P = 0.031) skin grafts was observed. These results demonstrate that induction of tolerance to class II antigens by BMT allows a short course of CsA to induce specific tolerance to fully allogeneic renal allografts.