Department of Burns and Cutaneous Surgery, Xijing Hospital, Fourth Military Medical University, Xi'an, Shaanxi Province, China.
PLoS One. 2012;7(8):e43825. doi: 10.1371/journal.pone.0043825. Epub 2012 Aug 29.
Vascularized bone marrow transplantation (VBMT) is widely accepted as an efficient means of establishing chimerism and inducing tolerance. However, the mechanism underlying is poorly understood. Recently, regulatory T cells (Tregs) have been shown to play an important role in regulating immune responses to allogeneic antigens. In this study, we explored the role of Tregs in the induction of tolerance in an allogeneic hind limb transplantation model.
METHODOLOGY/PRINCIPAL FINDINGS: Forty-eight Lewis rats were divided into 6 groups. They received isografts and allografts from Brown-Norway hind limbs. Recipients in groups 1 and 2 received isografts and those in the other groups received allografts. The bone components of donor limbs were kept intact in groups 1, 3, and 5 but removed before transplantation into groups 2, 4, and 6. Tapered cyclosporin A (CsA) was administered to recipients in groups 5 and 6 after transplantation. During the 100-day observation period, all isografts survived, but the allografts in groups 3 and 4 were rejected within 8 to 12 days. CsA-treated intact allografts survived rejection-free for more than 100 days, and CsA-treated allografts lacking bone elements were rejected within 2 months. Stable peripheral chimerism and myeloid chimerism were observed in group 5. Declining peripheral chimerism and a lack of myeloid chimerism were observed in group 6. Donor-specific Tregs were exclusively detected in both peripheral blood and in the spleens of long-term recipient rats in group 5, with an increased FoxP3 mRNA expression in the allografts. This was further demonstrated to be responsible for donor-specific hyporeactivity by in vitro one-way mixed lymphocyte reaction (MLR).
CONCLUSION/SIGNIFICANCE: Bone components in the allogeneic hind limbs can induce myeloid chimerism and donor-specific Tregs may be essential to tolerance induction. The bone-removal hind limb model may be a suitable counterpart to the induction of tolerance in the study of limb transplantation.
血管化骨髓移植（VBMT）被广泛认为是建立嵌合体和诱导耐受的有效手段。然而，其机制尚不清楚。最近，调节性 T 细胞（Tregs）已被证明在调节对同种异体抗原的免疫反应中发挥重要作用。在这项研究中，我们探讨了 Tregs 在同种异体后肢移植模型中诱导耐受中的作用。
方法/主要发现：48 只 Lewis 大鼠分为 6 组。它们接受了来自 Brown-Norway 后肢的同基因和同种异体移植物。第 1 组和第 2 组接受同基因移植物，其余组接受同种异体移植物。第 1、3 和 5 组保留供体肢体的骨成分，而第 2、4 和 6 组在移植前将其去除。第 5 和 6 组在移植后给予渐减环孢素 A（CsA）。在 100 天的观察期内，所有同基因移植物均存活，但第 3 和 4 组的同种异体移植物在 8 至 12 天内被排斥。CsA 治疗的完整同种异体移植物无排斥反应存活 100 天以上，而缺乏骨成分的 CsA 治疗同种异体移植物在 2 个月内被排斥。第 5 组观察到稳定的外周嵌合和髓系嵌合，而第 6 组观察到外周嵌合减少和缺乏髓系嵌合。第 5 组长期受体大鼠的外周血和脾脏中均检测到供体特异性 Tregs，同种异体移植物中 FoxP3 mRNA 表达增加。通过体外单向混合淋巴细胞反应（MLR）进一步证明其对供体特异性低反应性的负责。
结论/意义：同种异体后肢的骨成分可诱导髓系嵌合，而供体特异性 Tregs 可能对诱导耐受至关重要。去骨后肢模型可能是研究肢体移植中诱导耐受的合适对照。
