Monocyte-derived dendritic cells in multiple sclerosis: the effect of bacterial infection

We investigated whether monocyte-derived dendritic cells (MDDCs) generated in vitro from bacteria-infected MS patients modified autoreactive T cells activation patterns. T cell clones (TCCs) stimulated with MDDCs from infected MS patients responded with maximal proliferation, inducing IL-12, IL-17 and IFN-gamma secretion, at concentrations significantly lower than after incubation with MDDCs isolated from uninfected individuals and bacterial meningitis (BM) patients. Moreover, infected MDDCs promoted TCCs survival, and secreted more IL-12, IL-18, and IL-23. Finally, MDDCs from infected MS subjects showed higher expression of myeloid differentiation factor 88 (MyD88), as well as of HLA-DR, CD1a, CD80, CD86, CD273, CD40, CD83 and CCR7 when compared to MDDCs from uninfected MS individuals, and BM patients. Thus, activation of the innate immune system by microbial products in MS patients affects the generation MDDCs and their ability to modify autoreactive T cell activation patterns, which may be linked to MS relapse induction during bacterial infections.