Although it is recognized that systemic maternal immune responses influence the fetus, how local decidual and placental inflammation, in the absence of an infectious agent, impacts the developing fetal immune system is not understood. Developing a deeper understanding of decidual/placental inflammation will provide opportunities for the development of targeted therapeutics either in utero or once offspring are born. Thus, the long-term goals of this project are to understand how the in utero environment impacts the developing fetal immune system, and to assess the long-term immunological consequences. The central hypothesis is that sterile inflammation at the maternal-fetal interface (MFI) leads to skewing of the fetal immune system towards a pro- inflammatory phenotype. To understand how sterile inflammation affects the fetal immune system, Tisseel, a binary product where fibrinogen and thrombin are co-delivered to create rapid clotting, will be injected to the MFI of pregnant rhesus macaques (Macaca mulatta), resulting in clotting and placental infarct development, leading to necrosis and inflammation. Specific Aim 1: To test the hypothesis that Tisseel injection into the MFI leads to sterile inflammation of the decidua and placenta. Tisseel or sterile saline will be injected into the MFI in the late second trimester/early third trimester (~GD90) of pregnant rhesus macaques. At ~GD155, the placenta and fetus will be obtained and weighed, and the fetus will be euthanized. MFI tissues will be processed for histopathology, molecular and immunological analyses, including spectral flow cytometry, scRNA-seq and Spatial Transcriptomics. Specific Aim 2: To test the hypothesis that Tisseel injection into the MFI leads to fetal immune system programming towards a proinflammatory phenotype. At experimental delivery, the fetus will be euthanized, fetal tissues will be collected and mononuclear cell (MC) suspensions prepared. MCs will be analyzed for gene expression (scRNA-seq) and chromatin accessibility (scATAC-seq). Overall, the proposed project will address how sterile inflammation at the MFI impacts the developing immune system. Because the fetal immune system is pliable, it makes this developmental stage an attractive opportunity for targeted therapeutics that could prevent long-term health consequences. Completion of this K01 proposal will also allow me to gain training in the development and use of experimental NHP models of pregnancy complications, skills in advanced data analysis, and understanding of the fetal immune system. This will facilitate my transition into an independent investigator in maternal-fetal health.