Activation of Human Skin T Cells by Mammalian and Microbial Lipids Presented by CD1a

 描述（由申请人提供）：人T细胞库的显著部分不识别肽-MHC复合物，而是被与CD 1抗原呈递分子复合的脂质激活。CD 1a是人类四种表面表达的脂质抗原呈递分子之一，在表皮朗格汉斯细胞上以高水平组成性表达。在皮肤免疫系统和皮肤微生物组之间的界面处的CD 1a高朗格汉斯细胞的定位表明CD 1a脂质抗原呈递系统在皮肤免疫中的重要作用。我们最近的研究结果进一步支持了这一观点，即CD 1a限制性T细胞在健康个体的血液和皮肤中很常见，并且人类皮肤中存在的某些疏水脂质可以作为这些T细胞的抗原。在我们鉴定的脂质抗原中，有游离脂肪酸、蜡酯、甘油三酯和角鲨烯，它们都是人体皮脂的成分。这表明皮肤脂质除了提供屏障功能之外的新作用，即作为T细胞抗原。此外，我们的皮肤是大量微生物种群的家园，这些微生物种群与我们鉴定为CD 1a抗原的哺乳动物脂质相似，仅在烷基链立体化学（顺式/反式不饱和度）或精细结构（例如甲基分支，环丙烷化）方面有所不同。先前的研究表明，脂质链的微小结构变化会影响CD 1限制性T细胞的激活强度，我们现在计划系统地解决以下问题：1）使用生物物理方法（Biacore），如果CD 1a限制性TCR与负载有微生物脂质结构的CD 1a分子的结合亲和力高于与负载有哺乳动物类似物的那些分子的结合亲和力，2）确定CD 1a的脂质结合偏好，通过LC/MS分析在与结构上相关的脂质的确定混合物共孵育后从CD 1a洗脱的脂质，3）使用哺乳动物脂质和微生物类似物确定皮肤驻留T细胞的精细特异性。最后，由于异位性皮炎患者的受累皮肤已显示出微生物植物群的变化以及脂质组成的变化，我们将使用CD 1a四聚体确定与异位性皮炎患者的非病变皮肤相比，病变皮肤中CD 1a限制性T细胞的频率是否增加。这项研究与申请人成为独立研究者的目标是一致的。 皮肤免疫生物学领域。该提案的结果将为皮肤中脂质抗原对T细胞活化的调节以及脂质组成的变化如何影响T细胞活化提供有价值的见解。这与皮肤免疫学领域高度相关，并开辟了新的基于脂质的皮肤疾病干预模式。

 DESCRIPTION (provided by applicant): A significant fraction of the human T cell repertoire does not recognize peptide-MHC complexes, but instead is activated by lipids complexed to CD1 antigen presenting molecules. CD1a, which is one of four surface-expressed lipid antigen presenting molecules in humans, is constitutively expressed at high levels on epidermal Langerhans cells. The localization of CD1ahigh Langerhans cells at the interface between skin immune system and skin microbiome, suggests an important role for the CD1a lipid antigen presenting system in skin immunity. This notion is further supported by our recent findings that CD1a-restricted T cells are common in blood and skin of healthy individuals, and that certain hydrophobic lipids present in human skin can act as antigens for these T cells. Among the lipid antigens we identified are free fatty acids, waxesters, triglycerides and squalene, all components of human sebum. This indicates a novel role for skin lipids beyond providing barrier function, namely as T cell antigens. Moreover, our skin is home to a large microbial population, which harbor close analogs of the mammalian lipids we identified as CD1a antigens, differing only in alkyl chain stereochemistry (cis/trans unsaturations) or fine structure (e.g. methyl branching, cyclopropanation). Prior studies have shown that minor structural changes in lipid chains can affect the strength of activation of CD1-restricted T cells, and we now plan to systemically address the following: 1) if CD1a-restricted TCRs bind with higher affinity to CD1a molecules loaded with microbial lipid structures than those loaded with mammalian analogs, using biophysical methods (Biacore), 2) determine the lipid binding preference of CD1a, by analyzing by LC/MS the eluted lipids from CD1a after co-incubation with defined mixtures of structurally related lipids, 3) determine the fine-specificity of skin-resident T cells using mammalian lipids and microbial analogs. Last, because affected skin in atopic dermatitis patients has been shown to display a shift in microbial flora as well as changes in lipid composition, we will determine if the frequency of CD1a-restricted T cells is increased in lesional compared to non-lesional skin of atopic dermatitis patients using CD1a tetramers. This research is in direct line with the applicant's goal of becoming an independent investigator in the field of skin immunobiology. The results of this proposal will provide valuable insights in the regulation of T cell activation by lipid antigens in the skin, and how shifts in lipid composition may affect T cell activation. This is highly relevant to the field of skin immunology, and opens the way to new lipid-based modes of intervention in skin diseases.