IL-10 producing CD8 ⁺ CD122 ⁺ PD-1 ⁺ regulatory T cells are expanded by dendritic cells silenced for Allograft Inflammatory Factor-1

Allograft Inflammatory Factor-1 (AIF1) is a cytoplasmic scaffold protein that contains Ca ²⁺ binding EF-hand and PDZ interaction domains important for mediating intracellular signaling complexes in immune cells. The protein plays a dominant role in both macrophage- and dendritic cell (DC)-mediated inflammatory responses. This study now reports that AIF1 expression in DC is important in directing CD8 ⁺ T cell effector responses. Silencing AIF1 expression in murine CD11c ⁺ DC suppressed antigen-specific CD8 ⁺ T cell activation, marked by reduced CXCR3, IFNγ and Granzyme B expression, and restrained proliferation. These primed CD8 ⁺ T cells had impaired cytotoxic killing of target cells in vitro. In turn, studies identified that AIF1 silencing in DC robustly expanded IL-10 producing CD8 ⁺ CD122 ⁺ PD-1 ⁺ regulatory T cells that suppressed neighboring immune effector responses through both IL-10 and PD-1-dependent mechanisms. In vivo studies recapitulated bystander suppression of antigen-responsive CD4 ⁺ T cells by the CD8 ⁺ Tregs expanded from the AIF1 silenced DC. These studies further demonstrate that AIF1 expression in DC serves as a potent governor of cognate T cell responses and present a novel target for engineering tolerogenic DC-based immunotherapies.