Ondrej Stepanek is an expert in the field of T cell receptor (TCR) signaling and adaptive immunity. He has more than 15 years of experience in research on T cell biology, spanning molecular mechanisms of receptor signaling, thymic development, and effector and regulatory T cell responses. Following his doctoral training at Charles University and the Institute of Molecular Genetics (IMG) in Prague, he pursued postdoctoral research at the University Hospital Basel, where he made fundamental contributions to our understanding of TCR tolerance mechanisms. Since establishing the Laboratory of Adaptive Immunity at IMG in 2016, Dr. Stepanek has developed an internationally recognized research program that dissects how T cells integrate signals from their receptors and co-receptors to make fate decisions. His group has uncovered unique roles of co-receptor–bound LCK in helper and cytotoxic T cells, identified a new IL-17 receptor subunit critical for T cell-mediated autoimmune pathology, and revealed novel mechanisms governing self-tolerance and functional T-cell diversity. To directly connect mechanism to physiology, his team makes extensive use of animal models, including syngeneic tumor models, autoimmune models driven by IL-17 signaling, and thymic development models elucidating lineage choice and co-receptor/LCK control of self-reactivity. These approaches have enabled the lab to bridge molecular immunology with disease-relevant biology. O. Stepanek is the recipient of an ERC Starting Grant (2019) and an ERC Consolidator Grant (2025), the only ERC grants in the field of immunity and immunotherapy (LS6) ever awarded in Czechia, and an EMBO Installation Grant. He is also a laureate of the J.E. Purkyne Fellowship of the Czech Academy of Sciences and the Eastern Star Award of the European Federation of Immunological Societies. His laboratory regularly publishes in prestigious journals such as Nature Immunology, Nature Communications, EMBO Journal, eLife etc. and actively collaborates across Europe and beyond. In addition to leading cutting-edge research, O. Stepanek is deeply committed to mentoring the next generation of immunologists, having supervised more than 15 PhD and MSc students. He teaches immunology courses at Charles University and serves on national and international evaluation panels. He is regularly invited to speak at international conferences and seminars.