Priming of Myelin-Specific T Cells in the Absence of Dendritic Cells Results in Accelerated Development of Experimental Autoimmune Encephalomyelitis

Experimental autoimmune encephalomyelitis (EAE), the animal model of multiple sclerosis (MS), is predominantly mediated by pro-inflammatory CD4+ T cell responses to CNS antigens, including myelin proteolipid protein (PLP). Dendritic cells (DCs) are considered critical for inducing T cell responses against infectious agents, but the importance of DCs in priming self-reactive CD4+ T cells in autoimmune disease such as MS has been unclear. To determine the requirement of DCs in PLP-specific CD4+ T cell responses and EAE, we genetically deleted CD11c+ DCs in PLP T cell receptor (TCR) transgenic SJL mice constitutively. DC deficiency did not impair the development, selection or the pathogenic function of PLP-specific CD4+ T cells in these mice, and resulted in accelerated spontaneous EAE compared to DC sufficient controls. In addition, using a genetic approach to ablate DCs conditionally in SJL mice, we show that CD11c+ DCs were dispensable for presenting exogenous or endogenous myelin antigen to PLP-specific T cells and for promoting pro-inflammatory T cell responses and severe EAE. Our findings demonstrate that constitutive or conditional ablation of CD11c+ DCs diminished self-tolerance to PLP autoantigen. They further show that in the absence of DCs, non-DCs can efficiently present CNS myelin antigens such as PLP to self-reactive T cells, resulting in accelerated onset of spontaneous or induced EAE.