CD4 T cells with specificity to noninherited maternal antigen.

描述（由申请人提供）：妊娠期间母体和胎儿细胞的混合和双向转移创造了一个迷人的和高度相关的免疫耐受生理模型。虽然这种相互作用主要是从母体对胎儿表达的父亲抗原的耐受性的角度来解决的，但成熟的胎儿细胞也会遇到同样大量的免疫外来的非遗传性母体抗原。因此，调节途径可能在免疫细胞发育的最早阶段就已经存在，以维持对非遗传性母源抗原（NIMA）的耐受性。此外，考虑到母体细胞在后代中的持续微嵌合，这些耐受途径也可能长期维持。在这方面，已经有令人信服的证据表明，免疫识别和耐受NIMA和其他外来抗原从子宫开始接触。然而，仍然未知的是免疫细胞和分子途径，从而实现对NIMA和其他子宫内暴露抗原的耐受性。我们提出关键的科学瓶颈包括无法精确识别NIMA反应性免疫细胞，这是表征其分子表型所必需的，以及以抗原特异性的方式区分这些潜在罕见细胞与不相关特异性的工具。我们在初步的概念可行性研究中表明，这些限制可以通过转基因雌性小鼠来克服，这些雌性小鼠被改造成组成性和无处不在地表达定义的模型抗原，与非转基因雄性小鼠交配，将模型抗原转化为替代的NIMA。反过来，新开发的四聚体染色和富集技术允许以抗原特异性的方式跟踪具有替代NIMA特异性的内源性免疫细胞。使用这种方法，我们的初步发现

DESCRIPTION (provided by applicant): The intermingling and bi-directional transfer of maternal and fetal cells during gestation creates a fascinating and highly relevant physiological model of immune tolerance. Although this interaction has been primarily addressed from the perspective of maternal tolerance to paternal antigens expressed by the fetus, maturing fetal cells also encounter an equally vast array of noninherited maternal antigens that are immunologically foreign. Thus, regulatory pathways are likely in place beginning at the earliest stages of immune cell development to maintain tolerance to noninherited maternal antigen (NIMA). Furthermore, these tolerance pathways are also likely to be maintained long term given the increasingly appreciated sustained microchimerism of maternal cells in offspring. In this regard, there is already compelling evidence illustrating immune recognition and tolerance to NIMA and other foreign antigens with exposure beginning in utero. However, what remains unknown are the immune cell and molecular pathways whereby tolerance to NIMA and other in utero exposed antigens is achieved. We propose key scientific bottlenecks include the inability to precisely identify NIMA responsive immune cells essential for characterizing their molecular phenotype, and the tools for discriminating these potentially rare cells in an antigen specific fashion from those with irrelevant specificity. We show in initial proof of concept feasibility studies these limitations are overcome using transgenic female mice engineered to constitutively and ubiquitously express defined model antigens for mating with non transgenic males that transforms model antigens into surrogate NIMA. In turn, newly developed tetramer staining and enrichment techniques allow endogenous immune cells with surrogate NIMA specificity to be tracked in an antigen specific fashion. Using this approach, our initial findings show CD4 T cells with NIMA specificity are (i) found in the peripheral lymphoid tissue in adult mice, (ii) selectively enriched for Foxp3 expression with >2-fold higher levels compared with naive or noninherited paternal antigen exposed controls, and (iii) expand only modestly while retaining exaggerated Foxp3 expression after infection with recombinant Listeria monocytogenes engineered to express the same NIMA associated peptide as a pathogen associated antigen. Based on these initial findings, our overall hypothesis is physiological exposure to noninherited maternal antigen in utero triggers tolerance through the selective accumulation of suppressive Foxp3+ regulatory T cells with specificity to these immunologically foreign antigens. To investigate this hypothesis, two inter-related aims are proposed to establish the precise immune cell subset that dictates NIMA induced tolerance, and define the necessity for maternal cell microchimerism in tolerance phenotypes for CD4 T cells with NIMA specificity. The successful completion of the aims for this exploratory grant will unlock and establish the scientific framework for additional more in depth functional and mechanistic studies aimed at further unraveling this under appreciated aspect of immunological tolerance.