DataSheet_1_Depletion of donor dendritic cells ameliorates immunogenicity of both skin and hind limb transplants.docx

Acute cellular rejection remains a significant obstacle affecting successful outcomes of organ transplantation including vascularized composite tissue allografts (VCA). Donor antigen presenting cells (APCs), particularly dendritic cells (DCs), orchestrate early alloimmune responses by activating recipient effector T cells. Employing a targeted approach, we investigated the impact of donor-derived conventional DCs (cDCs) and APCs on the immunogenicity of skin and skin-containing VCA grafts, using mouse models of skin and hind limb transplantation. By post-transplantation day 6, skin grafts demonstrated severe rejections, characterized by predominance of recipient CD4 T cells. In contrast, hind limb grafts showed moderate rejection, primarily infiltrated by CD8 T cells. Notably, the skin component exhibited heightened immunogenicity when compared to the entire VCA, evidenced by increased frequencies of pan (CD11b-CD11c+), mature (CD11b-CD11c+MHCII+) and active (CD11b-CD11c+CD40+) DCs and cDC2 subset (CD11b+CD11c+ MHCII+) in the lymphoid tissues and the blood of skin transplant recipients. While donor depletion of cDC and APC reduced frequencies, maturation and activation of DCs in all analyzed tissues of skin transplant recipients, reduction in DC activities was only observed in the spleen of hind limb recipients. Donor cDC and APC depletion did not impact all lymphocyte compartments but significantly affected CD8 T cells and activated CD4 T in lymph nodes of skin recipients. Moreover, both donor APC and cDC depletion attenuated the Th17 immune response, evident by significantly reduced Th17 (CD4+IL-17+) cells in the spleen of skin recipients and reduced levels of IL-17E and lymphotoxin-α in the serum samples of both skin and hind limb recipients. In conclusion, our findings underscore the highly immunogenic nature of skin component in VCA. The depletion of donor APCs and cDCs mitigates the immunogenicity of skin grafts while exerting minimal impact on VCA.

急性细胞排斥反应仍是影响包括血管化复合组织异体移植（vascularized composite tissue allografts, VCA）在内的器官移植成功结局的重大障碍。供体抗原呈递细胞（antigen presenting cells, APCs），尤其是树突状细胞（dendritic cells, DCs），可通过激活受体效应T细胞调控早期同种免疫应答。本研究采用靶向策略，利用皮肤及后肢移植小鼠模型，探究了供体来源的经典树突状细胞（conventional DCs, cDCs）与抗原呈递细胞对皮肤及含皮肤的VCA移植物免疫原性的影响。移植后第6天，皮肤移植物出现严重排斥反应，以受体CD4阳性T细胞浸润为主；与之相反，后肢移植物仅表现为中度排斥，主要浸润细胞为CD8阳性T细胞。值得注意的是，与完整VCA移植物相比，皮肤组分展现出更高的免疫原性，这一点在皮肤移植受体的淋巴组织与血液中，泛树突状细胞（CD11b⁻CD11c⁺）、成熟树突状细胞（CD11b⁻CD11c⁺MHCII⁺）、活化树突状细胞（CD11b⁻CD11c⁺CD40⁺）以及cDC2亚群（CD11b⁺CD11c⁺MHCII⁺）的频率升高中得到验证。尽管去除供体cDC与APC可降低皮肤移植受体所有分析组织中DC的频率、成熟度与活化水平，但仅在后肢移植受体的脾脏中观察到DC活性的降低。去除供体cDC与APC并未影响所有淋巴细胞亚群，但可显著影响皮肤移植受体淋巴结中的CD8阳性T细胞与活化CD4阳性T细胞。此外，去除供体APC与cDC均可减弱Th17免疫应答，具体表现为皮肤移植受体脾脏中Th17（CD4⁺IL-17⁺）细胞的频率显著降低，以及皮肤与后肢移植受体血清样本中IL-17E与淋巴毒素α的水平下降。综上，本研究结果凸显了VCA中皮肤组分的高免疫原性特性。去除供体APC与cDC可减轻皮肤移植物的免疫原性，但对完整VCA的影响极小。