Defining the molecular signals driving thymic Treg development in humans.

• Applicants: Professorin Dr. Julia Polansky-Biskup; Dr. Harald Stachelscheid
• Subject Area: Immunology ; Cell Biology
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 527668591

The immunosuppressive CD4+ FOXP3+ regulatory T cell population (Treg) is key to imposing and maintaining immunological tolerance toward self-antigens as well as harmless non-self antigens. This function makes them a promising effector population for the use in immunosuppressive adoptive T cell therapy targeting autoimmunity and transplant rejection, which is currently intensively tested in pre-/clinical trials worldwide. Despite their critical importance, the molecular pathways involved in the physiological Treg development in humans have not been comprehensively elucidated, mainly due to the lack of suitable in vitro models, restricted access to the required human tissues and an underestimation of the epigenetic layer as an important driver of T cell lineage commitment. Therefore, this project aims at closing important gaps in the understanding of thymic Treg development in humans. We focus on the identification and functional validation of critical epigenetic and molecular players controlling Treg lineage choices in the human thymus. For this, we will profile the epigenomic state of ex vivo isolated human thymocyte subsets (incl. genome-wide DNA methylation signatures, DNA accessibility landscapes and transcriptomic profiles), which will reveal molecular candidates, such as transcription factors, chromatin modifiers and epigenetic switches. These candidates will subsequently be tested for their functional impact in a newly established in vitro T cell development model utilizing human induced pluripotent stem cells (hiPSCs) and innovative epi-/genetic editing approaches. Finally, from the knowledge gained, we will define a protocol, which will allow the reliable generation of hiPSC-derived Tregs in vitro and verify their identity, fitness and immunosuppressive capacity by deep phenotypic, molecular and functional profiling. These qualities will be benchmarked against profiles from classically-generated therapeutic Treg products. This project brings together experts from different disciplines (immunologists, stem cell scientists, molecular biologists, bioinformaticians and T cell therapy experts) and is built upon our own profound previous work in the respective scientific fields as well as on a well-established cooperation with clinicians providing access to the required human tissue samples. It is this unique combination of assembled scientific expertise from different fields and state-of-the-art technologies, which will facilitate the successful execution of this ambitious project. The results of this study will greatly advance our understanding of physiological thymic Treg generation in humans, a process key for the establishment and maintenance of a well-balanced immune system. Ultimately, the project could define a protocol to generate hiPSC-derived Tregs suitable for immunosuppressive adoptive T cell therapies.

• DFG Programme: Research Grants