Functional and Epigenetic Analysis of Th2 Heterogeneity

T细胞的一个亚群，称为Th2细胞，是产生过敏免疫反应所必需的。Th2细胞表达三种标志性细胞因子，IL-4、IL-5和IL-13，每种细胞因子在过敏病理中都有特定的作用。IL-4促进Th2细胞分化，在抗体类向IgE转化过程中起主导作用，IL-5是主要的嗜酸性粒细胞活性细胞因子，IL-13通过上调黏附分子和趋化因子来驱动富含嗜酸性粒细胞的组织炎症。 我们假设Th2谱系内的异质性将产生具有不同细胞因子表达、效应器功能和在疾病发病机制中作用的Th2亚群。利用多色流式细胞术，我们发现人CD4Th2亚群中有两个主要亚群：IL-5-Th2细胞和IL-5+Th2细胞，IL-5-Th2细胞共同表达IL-4和IL-13，IL-5+Th2细胞表达所有三种Th2细胞因子。这两个群体的Th2细胞可以在体外直接证明，也可以在T细胞克隆和短期细胞系中证明。值得注意的是，直接从非过敏受试者体外分离的Th2细胞中，只有15%是IL-5+Th2细胞。IL-5+Th2细胞具有高分化记忆性T细胞的表型标志，提示IL-5+和IL-5-Th2细胞分别为高分化Th2细胞和低分化Th2细胞。我们通过检测Th2细胞因子在一系列体外Th2分化过程中的共表达，进一步验证了这一假设。到第二轮时，三分之二的细胞表达IL-4或IL-13，但有10%的细胞表达IL-5。在所分析的5轮中的每一轮中，IL-5+相对于IL-5-Th2表型的获得都是一致的且明显延迟。对两个Th2亚群的微阵列转录图谱显示，大约150个差异表达基因在IL-5-和IL5+Th2亚群之间。 综上所述，这些发现表明Th2细胞由两个亚群组成：IL-5+和IL-5-Th2细胞，而IL-5+Th2细胞代表了高度分化的Th2细胞的一个表型独特的亚群。这些结果表明，IL-5+Th2细胞具有不同于IL-5-Th2细胞的功能特性，可能在变态反应性炎症中起着独特的作用。了解IL-5基因调控对于开发针对嗜酸性炎症的有效策略非常重要。

A subset of T cells, termed Th2 cells, is required for the generation of allergic immune responses. Th2 cells express three signature cytokines, IL-4, IL-5, and IL-13, each of which makes a specific contribution to allergic pathology. IL-4 drives Th2 differentiation and plays a dominant role in antibody class switching to IgE, IL-5 is the major eosinophil active cytokine, and IL-13 drives eosinophil-rich tissue inflammation though its upregulation of adhesions molecules and chemokines. We hypothesized heterogeneity within the Th2 lineage would yield Th2 subpopulations with different cytokine expression, effector functions and roles in disease pathogenesis. Using polychromatic flow cytometry, we found two dominant subpopulations within the human CD4 Th2 compartment: IL-5- Th2 cells, which co-expressed IL-4 and IL-13, and IL-5+ Th2 cells, which expressed all three Th2 cytokines. These two populations of Th2 cells could be demonstrated directly ex vivo as well as in T cell clones and short-term lines. Notably, only 15% of the Th2 cells isolated directly ex vivo from non-allergic subjects were IL-5+ Th2 cells. IL-5+ Th2 cells exhibited phenotypic markers of highly differentiated memory T cells, suggesting that the IL-5+ and IL-5- Th2 cells are more and less highly differentiated Th2 cells, respectively. We further tested this hypothesis by examining Th2 cytokine coexpression during serial rounds of in vitro Th2 differentiation. By the second round, two-thirds of the cells expressed IL-4 or IL-13, but <10% of the cells expressed IL-5. In each of the 5 rounds analyzed, there was a consistent and markedly delayed acquisition of the IL-5+ relative to the IL-5- Th2 phenotype. Microarray transcription profiling of the two Th2 subpopulations revealed approximately 150 differentially expressed genes between the IL-5- and IL5+ Th2 subpopulations. In summary, these findings demonstrate that Th2 cells consist of two subpopulations: IL-5+ and IL-5- Th2 cells, and that IL-5+ Th2 cells represent a phenotypically distinct subpopulation of highly differentiated Th2 cells. These results suggest that IL-5+ Th2 cells have different functional properties than IL-5- Th2 cells and may make a unique contribution to allergic inflammation. Understanding IL-5 gene regulation is important in developing effective strategies targeting eosinophilic inflammation.