A novel CD4+ T cell population expanded in SLE blood provides B cell help through IL10 and succinate

A better understanding of the mechanisms involved in human plasma cell differentiation will accelerate therapeutic target identification in autoantibody-mediated diseases such as Systemic Lupus Erythematosus (SLE). Here, we describe a novel CXCR5- CXCR3+ PD1hi CD4+ T cell ‘helper’ population distinct from follicular helper T cells (Tfh) and expanded in blood and inflamed kidneys of SLE patients. Upon activation, these cells express IFNand high levels of IL10. Additionally, they accumulate high amounts of mitochondrial ROS (mtROS) as the result of reverse electron transport (RET) fueled by succinate. These cells provide potent help to B cells through the synergistic effect of IL10 and succinate. Cells with similar phenotype and function are generated in vitro upon priming naïve CD4+ T cells with oxidized mitochondrial DNA (Ox mtDNA)-activated plasmacytoid dendritic cells (pDCs) in a PD1-dependent manner. Our results provide a novel mechanism for the initiation and/or perpetuation of extrafollicular humoral responses in SLE. 9 total samples; 3 groups of 3 biological replicates: control group Th0, co-culture group CpGA-pDC, and co-culture group Ox mtDNA-pDC