Achieving antigen-specific immune tolerance without systemic immunosuppression remains a major challenge in biomaterial-based immunotherapy. Here, we report a simple nanoparticle (NP)-based platform that enables a transient, B cell–targeted tolerance switch. NPs encapsulating metabolizable aryl hydrocarbon receptor (AhR) agonists—FICZ or ITE—preferentially accumulate in splenic marginal zone B cells and convert them into IL-10–producing regulatory B cells (Bregs). This study provides the first in vivo evidence that Bregs can directly present antigen and induce regulatory T cells (Tregs), establishing a NP-controlled Breg–Treg pathway. These Bregs promote antigen-specific Tregs expansion only when co-exposed to antigen, establishing time-gated, antigen-restricted immune regulation. By exploiting the rapid metabolism of AhR agonists, this system provides precise temporal control of tolerance induction while preserving vaccine responses. In mouse models, co-administration of FICZ-containing NP with antigen suppressed anti-drug antibody formation and ameliorated allergic inflammation. This NP platform demonstrates a strategy for safe, antigen-specific immunomodulation and offers a clinically adaptable framework for allergy and biotherapeutic tolerance.
Hosokawa et al. (Fri,) studied this question.