Functional analyses of dendritic subsets in immune regulation

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In this project, we examined functional differences of endocytoic conventional dendritic cells (DCs) with type I interferon-producing plasmacyotoid preDCs (P-preDCs) in immune regulations in terms of cytokine production, T cell activation, and expansion of regulatory T cells. The following results were obtained.1)Ly49Q is a member of the Ly49 family that is expressed on Gr-1^+ cells, but not on NK and NKT cells. Conventional DCs were found to be negative for Ly49Q, while bone marrow-derived DCs expressed at low level and upregulated by IFN. On the other hand, Ly49Q was expressed on CD11c^+B220^+Gr-1^+P-preDCs in peripheral lymphoid tissues. However, the expression level on P-preDCs were variable in bone marrow. This was ascribed to the difference in differentiation stage of P-preDCs, since Ly49Q was expressed spontaneously upon culture and Ly49Q^+P-preDCs produced larger amounts of IFN-α/β,IL-6 and IL-12 by CpG-ODN.2)CD25^+CD4^+ regulatory or suppressor Tcells (Tregs) is known to maintain immunological self-tolerance, preventing autoimmunity. Previously we have shown that Tregs proliferate and retain their antigen-dependent suppressive functions when the APCs are antigen-loaded mature dendritic cells (DCs). Using allogeneic polyclonal Tregs, DCs were demonstrated to effectively sustain expression of Foxp3 in Tregs and to be potent for the expansion of alloantigen-specific Tregs in the presence of IL-2. Moreover, those expanded Tregs were efficient to suppressed GvHD induced by CD25- CD4- T cells.3)We generated mice that harbor a targeted insertion of a primate DTR in the Langerin locus. LCs were effectively and selectively ablated in adult Langerin-DTR mice within 24 h after injection of DT. Reconstitution of the epidermal LC compartment in the steady state took at least 4 wk. Functional analysis of LC-depleted mice revealed that dermal DCs were able to mediate a cutaneous CHS response.