Interestingly our analyses of human PBMCs using a monoclonal

Interestingly, our analyses of human PBMCs using a monoclonal antibody against EBI2 showed that the expression pattern of human EBI2 is largely overlapping with that in mice. Especially Th17 sto products receptor showed homogeneous high expression of EBI2 compared with Th1 cells, which contained a fraction of cells negative for EBI2. Furthermore, when we analyzed histological sections of lesions from MS patients, we found expression of EBI2 restricted to mononuclear cells present within inflamed white matter regions. Most cells expressing EBI2 morphologically appeared as infiltrating macrophages. We found T cells that were clearly negative and T cells with strong expression of EBI2 in MS lesions. This finding is in accordance with our flow cytometry data showing that only a part of all T cells express EBI2 and the fact that MS lesions are known to be dominated by CD8 cells (Babbe et al., 2000), which are largely negative for EBI2. Because EBI2 is expressed on the major subsets of immune cells, and small molecule antagonists for EBI2 were recently described (Benned-Jensen et al., 2013, Gessier et al., 2014), EBI2 constitutes a tempting drug target reminiscent of the sphingosine-1-phosphate receptor superagonist fingolimod/Gilenya that is currently in clinical use for treatment of MS patients.
Experimental Procedures Detailed descriptions about mass spectrometry, single cell RT-PCR, and immunohistochemistry are provided in the Supplemental Information.
Author Contributions
Acknowledgments We thank Petra Adams, Alexei Nikolaev, Marina Snetkova, and Elena Zurkowski for excellent technical assistance and Sebastian Attig (TRON, Mainz) and Alexander Hobhberger (FZI, Mainz) for cell sorting. This work was supported by the Deutsche Forschungsgemeinschaft SFB/TR-128 TPA3 to N.W. and F.C.K., TPA7 to A.W., TPZ1 to T.K., and by SFB/TR-156 TP C01 to F.C.K. and A.W. S.C. was supported by the Italian Association for Cancer Research (AIRC). A.W.S., I.C., and J.Z. are employees of Novartis Pharma, Basel, Switzerland and some of them hold stock and/or stock options in their company.
Introduction Inflammation is the protective reaction of the body to infection, injury, or irritation with the aim to remove harmful stimuli such as pathogens, damaged cells, or allergic irritants and to initiate the healing process. Inflammatory abnormalities play a crucial role in the pathogenesis of many human diseases including autoimmune disorders such as type 1 diabetes, rheumatoid arthritis, or multiple sclerosis as well as cardiovascular diseases such as atherosclerosis or metabolic disease. Monocyte-derived macrophages are key mediators of the innate immune response and are central for the inflammation process (for recent reviews see [1], [2]). Based on functional properties macrophage phenotypes fall within a spectrum of two extremes [3]. First, pro-inflammatory macrophages (M1 phenotype or classically-activated macrophages) secrete pro-inflammatory cytokines and chemokines, thereby initiating and sustaining inflammation in order to fight microbes and infected cells. Second, the anti-inflammatory, pro-resolution macrophages (M2 phenotype or alternatively-activated macrophages) which are induced by anti-inflammatory factors such as IL-4 or IL-13 and promote resolution events such as clearance of apoptotic cells and tissue repair. For mounting an effective immune response by secretion of pro- or anti-inflammatory mediators and phagocytosis of invading pathogens or cellular debris during an infection, deployment of specific subsets of macrophages to the site of inflammation must be temporally and spatially strictly regulated. In a healthy environment this goal is achieved by a highly concerted production and release of different chemokines and the expression of their corresponding cognate receptors. Imbalances between the pro- and anti-inflammatory processes have been demonstrated to underlie the pathophysiology of autoimmunity and autoinflammation [4], [5].