Study of tolerance mechanism in a functional tolreance modrl of rat lung transplant

我们以前的研究表明，在肺移植的大鼠模型中，出现了自发的功能耐受。在该模型中观察到的耐受性可能是由于组织相容的微小差异。为了进一步验证这一模型，在该模型中检测了移植前供者特异性脾细胞输注(DST)对功能耐受状态的影响。F344大鼠在移植前-45天和-30天接受WKY脾细胞移植。对照组F344大鼠接受不含DSTs的肺移植。两组受者分别于移植后第7、14、21、49天实施安乐死，移植排斥反应(AR)分级为0~IV级。采用RT-PCR技术检测移植体内细胞因子基因转录水平。此外，受者在第35天接受同种异体和第三方皮肤移植，以评估全身耐受性的发展。对照组动物在前3周出现II-III期AR，随后在第49天自发恢复，I-II期AR。相比之下，DST动物在第14-21天出现了Ill-IV AR阶段，在第49天没有任何恢复的证据。WKY皮肤移植物在对照组动物中显示存活时间延长，但在DST动物中立即被排斥。结论：1)在WKY*F344肺移植模型中，DSTs不能提高同种异体移植物的存活率，但能诱导AR和消融耐受。2)DST诱导的AR与细胞因子免疫应答从以Th2为主向Th2为主的偏离有关。3)在该模型中，组织相容性以外的因素，如同种异体抗原暴露的途径、与同种异体肺移植物相关的同种异体抗原的数量或性质，参与了该模型中天然免疫反应向可接受性的偏离。

Our previous studies have shown that a spontaneous functional tolerance develops in a rat model of lung transplantation. The tolerance observed in this model may be due to the minor histocompatible differences. To further examine this model, the effect of pre-transplant donor-specific spleen cell transfusions (DSTs) was examined on the functional tolerance state in this model.F344 rats received WKY spleen cells on days-45 and-30 before transplantations. Control F344 rats received lung grafts without DSTs. Recipients in both groups were euthanized on day 7,14,21 and 49 post-transplant, and allograft rejection (AR) was graded stage 0-IV.Intragraft cytokine gene transcripts were examined using RT-PCR techniques. In addition, allogeneic and third party skin grafts were placed on recipients at day 35 to evaluate the development of systemic tolerance. Control animals showed stage II-III AR in the first 3 weeks followed by spontenous recovery with stage I-II AR on day 49. In contrast, DST animals showed stage Ill-IV AR by day14-21, without any evidence of recovery on day 49. WKY skin grafts showed prolonged survival in control animals, but were promptly rejected in DST animals. Intragraft cytokine gene expression in control animals was characterized by weak expression of IL-2 and high IL-10, while DST animals showed high levels of IL-2 transcripts.Conclusions : 1) Pre-transplant DSTs did not enhance allograft survival, but induced AR and ablated tolerance in the WKY*F344 lung transplant model. 2) The DST-induced AR was associated with a deviation of cytokine immune responses from a predominant Th2 to Th1.3) Factors other than histocompatibility, such as route of alloantigen exposure, amount or nature of alloantigens associated specifically with lung allografts, are involved in deviating native immune responses toward acceptance in this model.