Plege Annegret, Borns Katja, Baars Wiebke, Schwinzer Reinhard
Transplantationslabor, Klinik für Viszeral- und Transplantationschirurgie, Medizinische Hochschule Hannover, Hannover, Germany.
Transplantation. 2009 Apr 15;87(7):975-82. doi: 10.1097/TP.0b013e31819c85e8.
Genetic modification of pigs (e.g., transgenic expression of human complement regulatory molecules or inactivation of alpha1,3galactosyltransferase) enabled the development of promising strategies to overcome hyperacute rejection after pig-to-primate xenotransplantation. However, cellular rejection still remains a hurdle for successful xenograft survival. This report tested the hypothesis that overexpression of human negative costimulatory PD-Ligands (PD-L) in pig antigen presenting cells might be an approach to prevent human anti-pig T-cell responses.
The pig B-cell line L23 was transfected with the pIRES-AcGFP vector containing human PD-L1 or PD-L2. Stable transfectants (L23-PD-L1, L23-PD-L2 cells) were established and used for in vitro stimulation of purified human CD4+ T cells.
Human CD4+ T cells responded with significantly reduced proliferation to L23-PD-L1 or L23-PD-L2 cells and produced less IL-2, IFNgamma, TNFalpha, IL-4, and IL-5 than cells stimulated with mock-transfected B cells. The concentration of IL-10, however, was increased in CD4+ T cells responding to stimulation with PD-L1 or PD-L2 transfectants. Furthermore, in cultures of CD4+ T cells stimulated for 3 weeks with PD-L1 or PD-L2 transfectants a CD4+CD25(high)Foxp3+ subset showed up that effectively suppressed the activation of conventional CD4+ T cells.
These findings imply that PD-1/PD-Ligand pathways are interesting targets to prevent human anti-pig T-cell responses after xenotransplantation, and also suggests that PD-1/PD-Ligand interactions may play a role in the control of the activity and/or homeostasis of regulatory T cells.
猪的基因改造（例如，人补体调节分子的转基因表达或α1,3-半乳糖基转移酶的失活）使得开发出了有前景的策略来克服猪到灵长类动物异种移植后的超急性排斥反应。然而，细胞排斥仍然是异种移植物成功存活的一个障碍。本报告检验了这样一个假设，即在猪抗原呈递细胞中过表达人负性共刺激分子程序性死亡配体（PD-L）可能是一种预防人抗猪T细胞反应的方法。
用含有人类PD-L1或PD-L2的pIRES-AcGFP载体转染猪B细胞系L23。建立稳定转染子（L23-PD-L1、L23-PD-L2细胞）并用于体外刺激纯化的人CD4+ T细胞。
与用mock转染的B细胞刺激的细胞相比，人CD4+ T细胞对L23-PD-L1或L23-PD-L2细胞的增殖反应显著降低，并且产生的白细胞介素-2（IL-2）、干扰素γ（IFNγ）、肿瘤坏死因子α（TNFα）、白细胞介素-4（IL-4）和白细胞介素-5（IL-5）更少。然而，在用PD-L1或PD-L2转染子刺激的CD4+ T细胞中，白细胞介素-10（IL-10）的浓度增加。此外，在用PD-L1或PD-L2转染子刺激3周的CD4+ T细胞培养物中，出现了一个CD4+CD25（高）Foxp3+亚群，该亚群有效地抑制了传统CD4+ T细胞的活化。
这些发现表明，PD-1/PD-Ligand途径是预防异种移植后人抗猪T细胞反应的有趣靶点，并且还表明PD-1/PD-Ligand相互作用可能在调节性T细胞的活性和/或内环境稳定的控制中发挥作用。
