T cell fate is dictated by different antigen presenting cells in response to dietary versus gut epithelial...

We investigated whether T cell responses and antigen-presenting cell (APC) requirements in gut-draining lymph nodes differ by antigen source, diet versus epithelium. Using mice fed ovalbumin (OVA) or expressing secreted (s), cytosolic (c), or transmembrane (tm) epithelial OVA, we compared OVA-specific T cell fates. At baseline and after reovirus infection, T cell responses were comparable across models. However, helminth infection induced Th2 cell polarization in sOVA and tmOVA but not cOVA or OVA-fed mice. BATF3⁺ APCs were indispensable for CD4⁺ T cell proliferation only in cOVA mice yet drove Treg cell differentiation across all epithelial OVA models. In contrast, antigen presentation by RORγt⁺MHC-II⁺ APCs was exclusively required for Treg cell induction by dietary OVA. These distinct APC dependencies correlated with susceptibility to pathology elicited by dietary versus epithelial self-antigens. Thus, antigen origin and presentation context are integrated to shape T cell fate, a new framework for predicting gut immune outcomes.