Therefore, the DEC-205 receptor can deliver antigen to DCs for presentation to both CD4+ and CD8+ T cells, and when that is performed in the steady state it leads to deletional tolerance or anergy of the antigen-specific T cells. Targeting steady-state
buy BGB324 immature DCs with antigen-linked anti-DEC-205 antibody, apart from inducing anergy and deletion of cognate T cells [20,35], can also lead to the induction and/or expansion of Tregs[47,82]. Anti-DEC-205/OVA drove short-lived proliferation of OVA-specific CD4+ T cells in vivo and led to the induction of CD25+/CTLA-4+ T cells with regulatory properties which could suppress proliferation and IL-2 production of conventional CD4+ T cells in a dose-dependent manner [82]. This phenomenon was corroborated further in CD4+ and CD8+ T cell-driven hypersensitivity models, where suppression of immune responses could be achieved in vivo by the induction of CD4+CD25+ Tregs by antigen-linked anti-DEC-205. To investigate further whether DCs are able to induce Tregs from truly naive FoxP3- CD4+ T cells, peptide ligands were targeted to DCs through DEC-205 and FoxP3 expression was analysed PLX3397 research buy at the single-cell level [47]. In this study, which used T cells from Rag2−/− TCR transgenic mice to exclude pre-existing FoxP3+ cells, it was shown that the converted Tregs expressed FoxP3 just as
do natural Tregs. It was also demonstrated that minute antigen doses with suboptimal DC activation were necessary for Treg induction, which was enhanced further by the addition of transforming growth factor (TGF)-β or in the absence of IL-2. Importantly, these FoxP3+ Tregs could be expanded by immunogenic presentation of antigen and also retained their surface phenotype and suppressor activity. Recently, Yamazaki and Steinman reported that CD8+DEC205+ splenic DCs are particularly well equipped to induce FoxP3+ Tregs from FoxP3- precursors [45]. This occurs in the presence Pyruvate dehydrogenase of low doses of
antigen and requires TGF-β expressed by the DEC-205+ DCs themselves. This may explain partially why, in some cases, DC targeting by antigen-linked anti-DEC-205 antibody led to the conversion of conventional CD4+ T cells to CD25+CD4+ Tregs[47,82]. The therapeutic potential of DEC-205-mediated antigen delivery has begun to be explored in mouse models of type 1 diabetes [69,70]. The first such study utilized a CD4+ T cell-driven model in which mice express haemagglutinin (HA) under the control of the rat insulin promoter (INS) and an I-Ed-restricted TCR specific for HA110–120. These mice have a diabetes incidence of 40%. When treated with HA peptide-linked anti-DEC-205 repeatedly from birth until 12–16 weeks of age, diabetes was prevented in most animals.