Localization of memory CD8+ T cells to lymphoid or peripheral tissues is believed to correlate with proliferative capacity or effector function. Here we demonstrate that the fractalkine-receptor/CX3CR1 distinguishes memory CD8+ T cells with cytotoxic effector function from those with proliferative capacity, independent of tissue-homing properties. CX3CR1-based transcriptome and proteome-profiling defines a core signature of memory CD8+ T cells with effector function. We find CD62LhiCX3CR1+ memory T cells that reside within lymph nodes. This population shows distinct migration patterns and positioning in proximity to pathogen entry sites. Virus-specific CX3CR1+ memory CD8+ T cells are scarce during chronic infection in humans and mice but increase when infection is controlled spontaneously or by therapeutic intervention. This CX3CR1-based functional classification will help to resolve the principles of protective CD8+ T-cell memory.

Intrahepatic cholangiocarcinoma (ICC) is a highly malignant, heterogeneous cancer with poor treatment options. We found that mitochondrial dysfunction and oxidative stress trigger a niche favoring cholangiocellular overgrowth and tumorigenesis. Liver damage, reactive oxygen species (ROS) and paracrine tumor necrosis factor (Tnf) from Kupffer cells caused JNK-mediated cholangiocellular proliferation and oncogenic transformation. Anti-oxidant treatment, Kupffer cell depletion, Tnfr1 deletion, or JNK inhibition reduced cholangiocellular pre-neoplastic lesions. Liver-specific JNK1/2 deletion led to tumor reduction and enhanced survival in Akt/Notch- or p53/Kras-induced ICC models. In human ICC, high Tnf expression near ICC lesions, cholangiocellular JNK-phosphorylation, and ROS accumulation in surrounding hepatocytes are present. Thus, Kupffer cell-derived Tnf favors cholangiocellular proliferation/differentiation and carcinogenesis. Targeting the ROS/Tnf/JNK axis may provide opportunities for ICC therapy.

Regulatory myeloid immune cells, such as myeloid-derived suppressor cells (MDSCs), populate inflamed or cancer tissue and block immune cell effector functions. Lack of mechanistic insight 54 into MDSC suppressive activity and a marker for their identification hampered attempts to 55 overcome T cell-inhibition and unleash anti-cancer immunity. Here we report that human MDSCs 56 were characterized by strongly reduced metabolism and conferred this compromised metabolic 57 state to CD8 + T cells thereby paralyzing their effector functions. We identified accumulation of the dicarbonyl-radical methylglyoxal, generated by semicarbazide-sensitive amine oxidase (SSAO), to cause the metabolic phenotype of MDSCs and MDSC-mediated paralysis of CD8 + T cells. In a murine cancer model, neutralization of dicarbonyl-activity overcame MDSC-mediated T cell-suppression and together with checkpoint inhibition improved efficacy of cancer immune therapy. Our results identify the dicarbonyl methylglyoxal as marker metabolite for MDSCs that mediates T cell paralysis and can serve as target to improve cancer immune therapy. Results 92 Dormant metabolic phenotype in MDSCs 93Suppressive myeloid cells arise during chronic inflammation in tissues 17 , and tissue stromal cells 94 induce transition of monocytes into monocytic MDSCs 16 . We exploited this capacity of stromal cells to convert human peripheral blood monocytes into MDSCs, which are phenotypically similar 96 to CD14 + HLA-DR -/low suppressive myeloid cells directly isolated from cancer patients 16 , to characterize the mechanism of MDSC-mediated T cell suppression. Transcriptome analysis showed less than 200 differentially expressed genes between MDSCs and monocytes, which did not include surface molecules suitable for phenotypic discrimination or known immune suppressive mediators to explain their suppressive activity (supplementary table I-IV, Extended Data Fig. 1). Consistently, blockade of known immune suppressive mediators did not prevent MDSC-mediated T cell suppression (Extended Data Fig. 2). Surprisingly, we found downregulation of genes encoding glycolysis-related enzymes in MDSCs (Fig. 1a, and Extended Data Table V).Indeed, MDSCs showed reduced glucose uptake and Glut1 surface expression (Fig. 1b), the main transporter mediating glucose uptake in immune cells. As predicted from gene expression analysis, hexokinase activity was lower in MDSCs (Fig. 1c). To validate these results, we isolated CD14 + HLA-DR -/lo cells from tumor tissue of patients with hepatocellular carcinoma by enzymatic digestion followed by density centrifugation and flow cytometric cell sorting. We confirmed reduced glucose uptake and hexokinase activity in CD14 + HLA-DR -/low cells isolated from tumor tissue of cancer patients (Fig. 1d,e, and Extended Data Table VI), which are considered to represent MDSCs. Strikingly, MDSCs failed to utilize glucose for glycolysis and also showed reduced cellular bioenergetics, i.e. lower mitochondrial membrane potential quantified by the potentiometric mitochondrial ...

PMN-MDSCs (polymorphonuclear myeloid-derived suppressor cells) have been characterized in the context of malignancies. Here we found that PMN-MDSCs had the unique ability to restrain B cell accumulation during central nervous system (CNS) autoimmunity. Ly6G + cells were recruited to the CNS during experimental autoimmune encephalomyelitis (EAE), interacted with B cells that produced the cytokines GM-CSF and IL-6, and acquired properties of PMN-MDSCs in the CNS in a manner dependent on the signal transducer STAT3. Depletion of Ly6G + cells or dysfunction of Ly6G + cells through conditional ablation of STAT3 resulted in the selective accumulation of GM-CSF-producing B cells in the CNS compartment, which in turn promoted an activated microglial phenotype and failure to recover from EAE. The frequency of CD138 + B cells in the cerebrospinal fluid (CSF) of human patients with multiple sclerosis negatively correlated with the frequency of PMN-MDSCs in the CSF. Thus, PMN-MDSCs might selectively control the accumulation and cytokine secretion of B cells within the inflamed CNS.