間葉系幹細胞是成體幹細胞的一種，於成體組織中分佈數目少，具有自我更新以及分化成為多種特定功能體細胞的能力。近年來的研究結果顯示，間葉系幹細胞可逃脫異體T 細胞的識別並抑制異體T 細胞免疫活性的產生。活體外和活體實驗結果顯示，將間葉系幹細胞和T 細胞於活體外共同培養或注入活體時，間葉系幹細胞具有抑制allogeneicT細胞所引發的T細胞增殖反應和延緩異體皮膚移植的排斥反應發生的能力。有關間葉系幹細胞所調控的免疫細胞族群包括抗原呈現細胞、T 細胞和自然殺手細胞等。根據現有的實驗結果顯示，間葉幹系細胞所引發T 細胞的免疫抑制機制有許多，其中涵蓋了間葉系幹細胞缺乏免疫相關的表面分子、引發調節性T細胞產生、阻斷T細胞的細胞週期的進行、減少T 細胞tryptophan 胺基酸的合成及產生可溶性因子作用於T細胞上等。由於間葉系幹細胞具有免疫抑制的活性，使得間葉系幹細胞具有可被運用於移植和疾病治療上的潛力。這篇綜論主要是針對間葉系幹細胞的免疫調節活性及其未來在臨床醫學的應用做詳細的探討和介紹。

Mesenchymal stem cells (MSCs) are a rare but unique population in that they have selfrenewaland differentiation abilities and are able to replenish a variety of specific cell types.Evidence is emerging that MSCs escape recognition of alloreactive T cells and exert a hypoimmunogeniccharacter. MSCs have been shown to suppress activation of T cells in vitro andprolong skin allograft survival in vivo. MSCs modulate the immune function of cell populationsincluding antigen presenting cells, T cells, and natural killer cells. The available data indicate thatseveral mechanisms are involved in MSC-mediated immunosuppressive effects. The mechanismsthat mediate the immunosuppressive effects of MSCs involve the expression of low levels ofimmunophenotypes, promotion of the expansion of regulatory T cells, induction of cell divisionalarrest in T cells, creation of tryptophan depletion, and production of soluble immunomodulatoryfactors. These findings make MSCs theoretically suitable for transplantation and diseasetreatment. In this review, we discuss the mechanisms underlying MSCs' immunomodulatingproperties and their potential applications.