Apoptotic Cell-induced Tolerogenic Dendritic Cells Facilitate Development of CD4+ and CD8+ Regulatory T cell Subsets

Objective: Dendritic cells (DCs) play an important role in regulating T cell-mediated immune responses; however, the mechanisms of DC-mediated immune responses have not been fully elucidated. Regulatory T cells (Tregs) including CD4+ and CD8+ Tregs play an essential role in induction of immune tolerance in vivo. It is unclear how DCs regulate development of Tregs. Our objective is to observe whether or not apoptotic cell-induced tolerogenic DCs can affect development and differentiation of CD4+ and CD8+ regulatory T cells. Methods: CD11c+ DCs were sorted and isolated from spleen of C57BL/6J mice. DCs were incubated with apoptotic or fresh T cells for 24 hrs at 37°C. MOG-specific CD4+CD25T cells were isolated from 2D2 transgenic mice. Apoptotic or fresh T cell-treated DCs were loaded with MOG peptide and co-cultured with MOG-primed CD4+CD25T cells for 72 hrs at 37°C. Expression of signal molecules and cytokines in DCs and Tregs was detected using flow cytometry. Results: Apoptotic T cell-treated DCs express CD40, CD80, CD86 and MHC class II at low levels compared with those on DCs co-cultured with fresh T cells. Treatment of DCs with apoptotic T cells inhibits production of inflammatory cytokines such as IL-12 and IL-23, but facilitates production of anti-inflammatory cytokines including IL-10 and TGF-β, indicating a tolerogenic phenotype. In co-culture, apoptotic T cell-induced tolerogenic DCs facilitate development of multiple subsets of CD4+ and CD8+ regulatory T cells (Tregs) such as CD4+CD25+, CD4+CD127+ and CD8+CD122+ regulatory T cells, and modulate expression of multiple signal molecules including GARP, CD152, CD44, CD62L, CCR6 and CCR7 on CD4+ Tregs. Conclusions: It can be concluded that apoptotic cell-induced tolerogenic DCs exert an immune-regulatory effect by facilitating development of both CD4+ and CD8+ Treg subpopulations. These results may reveal a new cellular mechanism of tolerogenic DCs induced by apoptotic cells to modulate inflammatory responses.