Department of Molecular and Cellular Physiology, Louisiana State University Health Sciences Center, Shreveport, Louisiana, United States of America.
PLoS One. 2009 Nov 23;4(11):e7840. doi: 10.1371/journal.pone.0007840.
Donor-specific blood transfusion (DST) prior to solid organ transplantation has been shown to induce long-term allograft survival in the absence of immunosuppressive therapy. Although the mechanisms underlying DST-induced allograft tolerance are not well defined, there is evidence to suggest DST induces one or more populations of antigen-specific regulatory cells that suppress allograft rejection. However, neither the identity nor the regulatory properties of these tolerogenic lymphocytes have been reported. Therefore, the objective of this study was to define the kinetics, phenotype and suppressive function of the regulatory cells induced by DST alone or in combination with liver allograft transplantation (LTx).
METHODOLOGY/PRINCIPAL FINDINGS: Tolerance to Dark Agouti (DA; RT1(a)) rat liver allografts was induced by injection (iv) of 1 ml of heparinized DA blood to naïve Lewis (LEW; RT1(l)) rats once per week for 4 weeks prior to LTx. We found that preoperative DST alone generates CD4(+) T-cells that when transferred into naïve LEW recipients are capable of suppressing DA liver allograft rejection and promoting long-term survival of the graft and recipient. However, these DST-generated T-cells did not express the regulatory T-cell (Treg) transcription factor Foxp3 nor did they suppress alloantigen (DA)-induced activation of LEW T-cells in vitro suggesting that these lymphocytes are not fully functional regulatory Tregs. We did observe that DST+LTx (but not DST alone) induced the time-dependent formation of CD4(+)Foxp3(+) Tregs that potently suppressed alloantigen-induced activation of naïve LEW T-cells in vitro and liver allograft rejection in vivo. Finally, we present data demonstrating that virtually all of the Foxp3-expressing Tregs reside within the CD4(+)CD45RC(-) population whereas in which approximately 50% of these Tregs express CD25.
CONCLUSIONS/SIGNIFICANCE: We conclude that preoperative DST, in the absence of liver allograft transplantation, induces the formation of CD4(+) T-cells that are not themselves Tregs but give rise directly or indirectly to fully functional CD4(+)CD45RC(-)Foxp3(+)Tregs when transferred into MHC mismatched recipients prior to LTx. These Tregs possess potent suppressive activity and are capable of suppressing acute liver allograft rejection. Understanding the mechanisms by which preoperative DST induces the generation of tolerogenic Tregs in the presence of alloantigens may lead to the development of novel antigen-specific immunological therapies for the treatment of solid organ rejection.
在实体器官移植前进行供体特异性输血（DST）已被证明可在没有免疫抑制治疗的情况下诱导长期同种异体移植物存活。尽管 DST 诱导同种异体移植耐受的机制尚未完全明确，但有证据表明 DST 诱导产生一种或多种抗原特异性调节细胞群，从而抑制同种异体移植物排斥反应。然而，这些耐受原性淋巴细胞的身份和调节特性尚未报道。因此，本研究的目的是定义单独或与肝移植（LTx）联合使用 DST 诱导的调节细胞的动力学、表型和抑制功能。
方法/主要发现：通过每周一次向 naive Lewis（LEW；RT1(l)）大鼠静脉注射 1 毫升肝素化 Dark Agouti（DA；RT1(a)）血液，在 LTx 前 4 周诱导对 Dark Agouti（DA）大鼠肝同种异体移植物的耐受性。我们发现，术前 DST 单独产生 CD4(+)T 细胞，当转移到 naive LEW 受者中时，能够抑制 DA 肝同种异体移植物排斥反应，并促进移植物和受者的长期存活。然而，这些 DST 产生的 T 细胞不表达调节性 T 细胞（Treg）转录因子 Foxp3，也不抑制体外 DA 诱导的 LEW T 细胞活化，表明这些淋巴细胞不是完全功能的调节性 Tregs。我们确实观察到，DST+LTx（但不是 DST 单独）诱导了 CD4(+)Foxp3(+)Tregs 的时间依赖性形成，这些 Tregs 在体外强烈抑制了 naive LEW T 细胞的同种异体抗原诱导的活化，并抑制了体内肝同种异体移植物排斥反应。最后，我们提供的数据表明，几乎所有表达 Foxp3 的 Tregs 都存在于 CD4(+)CD45RC(-)群体中，而其中约 50%的 Tregs 表达 CD25。
结论/意义：我们得出结论，术前 DST 在没有肝移植的情况下诱导形成 CD4(+)T 细胞，这些 T 细胞本身不是 Tregs，但在 MHC 错配受者接受 LTx 前直接或间接产生完全功能的 CD4(+)CD45RC(-)Foxp3(+)Tregs。这些 Tregs 具有强大的抑制活性，能够抑制急性肝同种异体移植物排斥反应。了解术前 DST 在同种抗原存在下诱导耐受原性 Tregs 产生的机制，可能会导致开发针对实体器官排斥反应的新型抗原特异性免疫治疗方法。
