Kusaka S, Grailer A P, Fechner J H, Jankowska-Gan E, Oberley T, Sollinger H W, Burlingham W J
Department of Surgery, University of Wisconsin, Madison, WI 53792, USA.
J Immunol. 2000 Feb 15;164(4):2240-7. doi: 10.4049/jimmunol.164.4.2240.
The recognition of allo-MHC and associated peptides on the surface of graft-derived APC by host T cells (direct pathway allorecognition) plays an important role in acute rejection after organ transplantation. However, the status of the direct pathway T cells in stable long term transplants remains unclear. To detect alloreactive T cell clones in PBL and the allograft during the transplant tolerance, we utilized RT-PCR instead of functional assays, which tend to underestimate their in vivo frequencies. We established alloreactive CD4+ and CD8+ T cell clones from peripheral blood sampled during the stable tolerance phase of a patient whose graft maintained good function for 9 years, 7 without immunosuppression. We analyzed the sequence of TCR Vbeta and Valpha genes and made clonotype-specific probes that allowed us to detect each clone in peripheral blood or biopsy specimens obtained during a 1-year period before and after the rapid onset of chronic rejection. We found an unexpectedly high level of donor HLA-specific T cell clonotype mRNA in peripheral blood during the late tolerance phase. Strong signals for two CD4+ clonotypes were detected in association with focal T cell infiltrates in the biopsy. Chronic rejection was associated with a reduction in direct pathway T cell clonotype mRNA in peripheral blood and the graft. Our data are inconsistent with the hypothesis that direct pathway T cells are involved only in early acute rejection events and suggest the possibility that some such T cells may contribute to the maintenance of peripheral tolerance to an allograft.
宿主T细胞对移植物来源的抗原呈递细胞（APC）表面的同种异体MHC及相关肽的识别（直接途径同种异体识别）在器官移植后的急性排斥反应中起重要作用。然而，在长期稳定移植中直接途径T细胞的状态仍不清楚。为了在移植耐受期间检测外周血淋巴细胞（PBL）和同种异体移植物中的同种异体反应性T细胞克隆，我们采用了逆转录聚合酶链反应（RT-PCR）而非功能测定法，因为功能测定法往往会低估它们在体内的频率。我们从一名移植物保持良好功能达9年（其中7年未进行免疫抑制）的患者稳定耐受期采集的外周血中建立了同种异体反应性CD4⁺和CD8⁺T细胞克隆。我们分析了TCR Vβ和Vα基因的序列，并制备了克隆型特异性探针，使我们能够在慢性排斥反应快速发作前后1年期间采集的外周血或活检标本中检测每个克隆。我们发现在耐受后期外周血中供体HLA特异性T细胞克隆型mRNA水平出乎意料地高。在活检中检测到与局灶性T细胞浸润相关的两种CD4⁺克隆型的强信号。慢性排斥反应与外周血和移植物中直接途径T细胞克隆型mRNA的减少有关。我们的数据与直接途径T细胞仅参与早期急性排斥反应事件的假说不一致，并提示某些此类T细胞可能有助于维持对外周同种异体移植物的耐受的可能性。
