Highly differentiated IL5+ Th2 cells in food allergy and eosinophilic GI disease

嗜酸性粒细胞性胃肠疾病是一组以胃肠道嗜酸性粒细胞炎症为特征的食物过敏相关疾病。在过去的20年里，EGID的发病率急剧增加，特别是嗜酸性食管炎（EoE），但也有嗜酸性胃肠炎（EGE）。EGID患者通常有许多食物过敏，并且疾病随着基于氨基酸的无过敏原元素饮食的建立而缓解。总之，这表明EGID是食物过敏原驱动的嗜酸性炎症性肠道疾病。 在我们以前的工作中，我们已经证明IL-5+ Th 2细胞与EGID（嗜酸性食物过敏）有关，但与过敏性食物过敏无关。我们进一步将这些IL-5+ Th 2细胞表征为更高度分化的Th 2细胞，其是多轮抗原刺激的产物。研究过敏性炎症小鼠模型的其他研究小组已经确定了类似的IL-5+ Th 2细胞具有更大的促炎功能。这些IL-5+ Th 2细胞被称为致病性效应Th 2（peTh 2）细胞，以强调它们在引起疾病中的功能。总之，这些发现表明，食物过敏原驱动的IL-5+ peTh 2细胞是驱动过敏性嗜酸性粒细胞炎症的主要途径。 在过去的一年中，我们已经确定了这些peth 2细胞的表型标记，这有助于功能研究以及组织样本中的识别。充分描述的Th 2标志物CRTH 2与造血前列腺素合酶（hPGDS）或CD 161的组合鉴定了IL-5亮CD 4 T细胞群。在EGID和特应性皮炎中，这些peTh 2细胞的频率与外周血嗜酸性粒细胞计数密切相关，表明该细胞群驱动血液嗜酸性粒细胞增多。此外，我们已经表明，IL-5+ Th 2表达肠组织归巢受体，并在EGID中归巢到肠组织。在多种测定系统中，peTh 2细胞具有比IL-5-Th 2细胞更大的功能活性。这表明，peTh 2亚群是驱动过敏性嗜酸性粒细胞炎症的主要Th 2群体。 我们还表明，Th 2细胞，特别是peth 2细胞，对雷帕霉素（mTOR）抑制剂的分子靶标，如雷帕霉素和Torin 1高度敏感。在0.25-10 nM的浓度范围内，雷帕霉素对IL-5+ peTh 2细胞的增殖抑制显著大于IL-5-Th 2或Th 1细胞。IL-5+ Th 2细胞表现出增强的S6核糖体蛋白磷酸化，表明mTORC 1通路在该亚群中优先激活。使用mTORC 1途径基因的RNA抑制证实了mTORC 1途径在peTh 2细胞增殖中的关键作用。这些结果表明，peTh 2细胞具有高度代谢活性，因此上调了mTORC 1途径。peth 2细胞的这种mTORC 1上调导致其对mTOR抑制剂的更高敏感性。

Eosinophilic gastrointestinal disorders (EGIDs) are a group of food allergy related diseases characterized by eosinophilic inflammation of the gastrointestinal tract. In the past 20 years, there has been a dramatic increase in the incidence of EGIDs, particularly eosinophilic esophagitis (EoE), but also eosinophilic gastroenteritis (EGE). EGID patients often have numerous food hypersensitivities, and the disease goes into remission with the institution of an amino acid based allergen-free elemental diet. In sum, this suggests that EGID is a food allergen driven eosinophilic inflammatory gut disease. In our previous work, we have demonstrated that IL-5+ Th2 cells are associated with EGID (eosinophilic food allergy), but not anaphylactic forms of food allergy. We have further characterized these IL-5+ Th2 cells as more highly differentiated Th2 cells that are the product of multiple rounds of antigenic stimulus. Other research groups working with mouse models of allergic inflammation have identified similar IL-5+ Th2 cells as having greater pro-inflammatory function. These IL-5+ Th2 cells have been termed pathogenic effector Th2 (peTh2) cells to emphasize their function in causing disease. In sum, these findings suggest that food allergen-driven IL-5+ peTh2 cells are the major pathway driving allergic eosinophilic inflammation. In the past year we have characterized phenotypic markers for these peTh2 cells, which facilitate both functional studies as well as their identification in tissue samples. The combination of the well-described Th2 marker CRTH2 with either hematopoietic prostaglandin synthase (hPGDS) or CD161 identified an IL-5 bright CD4 T cell population. In both EGID and atopic dermatitis, the frequency of these peTh2 cells was tightly correlated to peripheral blood eosinophil count, suggesting that this cell population is driving blood eosinophilia. Additionally, we have shown that IL-5+ Th2 express gut tissue homing receptors and home to gut tissue in EGID. In a variety of assay systems, peTh2 cells have greater functional activity than IL-5- Th2 cells. This indicates that the peTh2 subpopulation is a major Th2 population driving allergic eosinophilic inflammation. We have also shown that Th2 cells, and in particular peTh2 cells, are highly sensitive to molecular target of rapamycin (mTOR) inhibitors, such as rapamycin and Torin 1. Rapamycin inhibition of proliferation is significantly greater for IL-5+ peTh2 vs. either IL-5- Th2 or Th1 cells, at concentrations ranging from 0.25-10 nM. IL-5+ Th2 cells demonstrated enhanced S6 ribosomal protein phosphorylation, indicating that the mTORC1 pathway is preferentially activated in this subpopulation. The key role of the mTORC1 pathway in peTh2 cell proliferation was confirmed using RNA inhibition of mTORC1 pathway genes. These results demonstrate that peTh2 cells are highly metabolically active and as such have upregulated the mTORC1 pathway. This mTORC1 upregulation by peTh2 cells results in their greater sensitivity to mTOR inhibitors.