Sekiya Takashi, Yoshimura Akihiko
Department of Microbiology and Immunology, Keio University School of Medicine, 35 Shinanomachi, Shinjyuku-ku, Tokyo, 160-8582, Japan.
Methods Mol Biol. 2016;1344:183-91. doi: 10.1007/978-1-4939-2966-5_10.
CD4(+) T cells play central roles in adaptive immunity, driving appropriate immune responses to invading pathogens of diverse types. Four major CD4(+) T cell subsets, Th1, Th2, Th17, and Treg cells are differentiated from naïve CD4(+) T cells upon ligation of their T cell receptors with antigens, depending on the cytokines they receive. Th1 cells, which are induced by IL-12 and IFN-γ, mediate host defense against intracellular pathogens by exclusively expressing IFN-γ. Th2 cells, which are induced by IL4, secrete IL-4, IL-5, and IL-13, and protect hosts from helminths. IL-6 plus TGF-β induces Th17 cells, another Th subset identified relatively recently, express IL-17 and play important roles in the eradication of extracellular bacteria and fungi. Treg cells, which play central roles in immune suppression, are composed of either thymus-derived Treg cells (tTreg cells), which are directly developed from CD4-single positive (CD4-SP) cells in the thymus, or peripherally derived Treg cells (pTreg cells), which are induced by TGF-β plus IL-2 from naïve CD4(+) T cells. Although the regulated induction of Th cells results in proper eradication of pathogens, their excess activation results in various immune-associated diseases. For example, aberrant activation of Th1 and Th17 has been implicated in autoimmune diseases, excess Th2 activity causes atopic diseases, and impaired function of Treg cells due to abrogation of Foxp3 has been shown to cause fatal inflammatory disorders both in human and in mouse. The methods for in vitro differentiation of each Th subset described above are presented here. We hope these methods will facilitate understanding of differentiation and function of CD4(+) T cells and pathogenesis of various inflammatory diseases.
CD4(+) T细胞在适应性免疫中发挥核心作用，驱动针对多种入侵病原体的适当免疫反应。四大主要CD4(+) T细胞亚群，即Th1、Th2、Th17和调节性T（Treg）细胞，在其T细胞受体与抗原结合后，根据所接收的细胞因子，从初始CD4(+) T细胞分化而来。由白细胞介素12（IL-12）和干扰素γ（IFN-γ）诱导产生的Th1细胞，通过特异性表达IFN-γ介导宿主对细胞内病原体的防御。由IL-4诱导产生的Th2细胞分泌IL-4、IL-5和IL-13，保护宿主抵御蠕虫。IL-6加转化生长因子β（TGF-β）诱导产生Th17细胞，这是一个相对较新发现的Th亚群，表达IL-17并在清除细胞外细菌和真菌中发挥重要作用。在免疫抑制中起核心作用的Treg细胞，由胸腺来源的Treg细胞（tTreg细胞）或外周来源的Treg细胞（pTreg细胞）组成，tTreg细胞直接由胸腺中的CD4单阳性（CD4-SP）细胞发育而来，pTreg细胞则由初始CD4(+) T细胞接受TGF-β加IL-2诱导产生。尽管Th细胞的调节性诱导能导致病原体的适当清除，但它们的过度激活会引发各种免疫相关疾病。例如，Th1和Th17的异常激活与自身免疫性疾病有关，Th2活性过高会导致特应性疾病，而因叉头框蛋白3（Foxp3）缺失导致的Treg细胞功能受损已被证明在人和小鼠中都会引发致命的炎症性疾病。本文介绍了上述各Th亚群的体外分化方法。我们希望这些方法将有助于理解CD4(+) T细胞的分化和功能以及各种炎症性疾病的发病机制。
