ABSTRACT Regulatory T cells (Tregs) are fundamental to immune homeostasis, maintaining peripheral tolerance and preventing pathological autoimmunity across vertebrate species. The recent publication, “Beyond FoxP3: Identification of a Chicken Regulatory T Cell Signature,” in the European Journal of Immunology by Naumann et al., addresses a critical gap in comparative immunology by providing a comprehensive phenotypic and transcriptional characterization of chicken Treg cells. This commentary will situate the study within the historical context of Treg research, underscore the specific challenges in avian Treg characterization, and highlight the work's transformative implications for both basic immunology and applied poultry science.