Antigenic strength controls the generation of antigen‐specific IL‐10‐secreting T regulatory cells

Abstract

Administration of peptides i.n. induces peripheral tolerance in Tg4 myelin basic protein‐specific TCR‐Tg mice. This is characterized by the generation of anergic, IL‐10‐secreting CD4⁺ T cells with regulatory function (IL‐10 Treg). Myelin basic protein Ac1–9 peptide analogs, displaying a hierarchy of affinities for H‐2 A^u (Ac1–9[4K]<<[4A]<[4Y]), were used to investigate the mechanisms of tolerance induction, focusing on IL‐10 Treg generation. Repeated i.n. administration of the highest affinity peptide, Ac1–9[4Y], provided complete protection against EAE, while i.n. Ac1–9[4A] and Ac1–9[4K] treatment resulted in only partial protection. Ac1–9[4Y] was also the most potent stimulus for IL‐10 Treg generation. Although i.n. treatment with Ac1–9[4A] gave rise to IL‐10‐secreting CD4⁺ T cells, the population as a whole was also capable of secreting IFN‐γ after an in vitro recall response to Ac1–9[4A] or [4Y]. In addition to IL‐10 production, other facets of tolerance, namely, anergy and suppression (both in vitro and in vivo), were affinity dependent, with i.n. Ac1–9[4Y]‐, [4A]‐ or [4K]‐treated CD4⁺ T cells being the most, intermediate and least anergic/suppressive, respectively. These findings demonstrate that the generation of IL‐10 Treg in vivo is driven by high signal strength.