The renin-angiotensin-aldosterone system (RAAS) is a key hormonal system regulating blood pressure. However, expression of RAAS components has recently been detected in immune cells, and the RAAS has been implicated in several mouse models of autoimmune disease. Here, we have identified Ang II as a paracrine mediator, sustaining inflammation in the CNS in the EAE mouse model of MS via TGF-β. Ang II type 1 receptors (AT1Rs) were found to be primarily expressed in CNS-resident cells during EAE. In vitro, astrocytes and microglia responded to Ang II treatment by inducing TGF-β expression via a pathway involving the TGF-β–activating protease thrombospondin-1 (TSP-1). TGF-β upregulation in astrocytes and microglia during EAE was blocked with candesartan (CA), an inhibitor of AT1R. Treatment of EAE with CA ameliorated paralysis and blunted lymphocyte infiltration into the CNS, outcomes that were also seen with genetic ablation of AT1Ra and treatment with an inhibitor of TSP-1. These data suggest that AT1R antagonists, frequently prescribed as antihypertensives, may be useful to interrupt this proinflammatory, CNS-specific pathway in individuals with MS.
Tobias V. Lanz, Zhaoqing Ding, Peggy P. Ho, Jian Luo, Ankur N. Agrawal, Hrishikesh Srinagesh, Robert Axtell, Hui Zhang, Michael Platten, Tony Wyss-Coray, Lawrence Steinman
Evan Nair-Gill, Stephanie M. Wiltzius, Xiao X. Wei, Donghui Cheng, Mireille Riedinger, Caius G. Radu, Owen N. Witte
Abetalipoproteinemia (ABL) is a rare Mendelian disorder of lipid metabolism due to genetic deficiency in microsomal triglyceride transfer protein (MTP). It is associated with defects in MTP-mediated lipid transfer onto apolipoprotein B (APOB) and impaired secretion of APOB-containing lipoproteins. Recently, MTP was shown to regulate the CD1 family of lipid antigen-presenting molecules, but little is known about immune function in ABL patients. Here, we have shown that ABL is characterized by immune defects affecting presentation of self and microbial lipid antigens by group 1 (CD1a, CD1b, CD1c) and group 2 (CD1d) CD1 molecules. In dendritic cells isolated from ABL patients, MTP deficiency was associated with increased proteasomal degradation of group 1 CD1 molecules. Although CD1d escaped degradation, it was unable to load antigens and exhibited functional defects similar to those affecting the group 1 CD1 molecules. The reduction in CD1 function resulted in impaired activation of CD1-restricted T and invariant natural killer T (iNKT) cells and reduced numbers and phenotypic alterations of iNKT cells consistent with central and peripheral CD1 defects in vivo. These data highlight MTP as a unique regulator of human metabolic and immune pathways and reveal that ABL is not only a disorder of lipid metabolism but also an immune disease involving CD1.
Sebastian Zeissig, Stephanie K. Dougan, Duarte C. Barral, Yvonne Junker, Zhangguo Chen, Arthur Kaser, Madelyn Ho, Hannah Mandel, Adam McIntyre, Susan M. Kennedy, Gavin F. Painter, Natacha Veerapen, Gurdyal S. Besra, Vincenzo Cerundolo, Simon Yue, Sarah Beladi, Samuel M. Behar, Xiuxu Chen, Jenny E. Gumperz, Karine Breckpot, Anna Raper, Amanda Baer, Mark A. Exley, Robert A. Hegele, Marina Cuchel, Daniel J. Rader, Nicholas O. Davidson, Richard S. Blumberg
The inhibitory receptor programmed death 1 (PD-1) is upregulated on antigen-specific CD8+ T cells during persistent viral infections. Interaction with PD-1 ligand 1 (PD-L1) contributes to functional exhaustion of responding T cells and may limit immunopathology during infection. PD-L1 is expressed on both hematopoietic and nonhematopoietic cells in tissues. However, the exact roles of PD-L1 on hematopoietic versus nonhematopoietic cells in modulating immune responses are unclear. Here we used bone marrow chimeric mice to examine the effects of PD-L1 deficiency in hematopoietic or nonhematopoietic cells during lymphocytic choriomeningitis virus clone 13 (LCMV CL-13) infection. We found that PD-L1 expression on hematopoietic cells inhibited CD8+ T cell numbers and function after LCMV CL-13 infection. In contrast, PD-L1 expression on nonhematopoietic cells limited viral clearance and immunopathology in infected tissues. Together, these data demonstrate that there are distinct roles for PD-L1 on hematopoietic and nonhematopoietic cells in regulating CD8+ T cell responses and viral clearance during chronic viral infection.
Scott N. Mueller, Vijay K. Vanguri, Sang-Jun Ha, Erin E. West, Mary E. Keir, Jonathan N. Glickman, Arlene H. Sharpe, Rafi Ahmed
Neutrophils are a major component of the innate immune response. Their homeostasis is maintained, in part, by the regulated release of neutrophils from the bone marrow. Constitutive expression of the chemokine CXCL12 by bone marrow stromal cells provides a key retention signal for neutrophils in the bone marrow through activation of its receptor, CXCR4. Attenuation of CXCR4 signaling leads to entry of neutrophils into the circulation through unknown mechanisms. We investigated the role of CXCR2-binding ELR+ chemokines in neutrophil trafficking using mouse mixed bone marrow chimeras reconstituted with Cxcr2–/– and WT cells. In this context, neutrophils lacking CXCR2 were preferentially retained in the bone marrow, a phenotype resembling the congenital disorder myelokathexis, which is characterized by chronic neutropenia. Additionally, transient disruption of CXCR4 failed to mobilize Cxcr2–/– neutrophils. However, neutrophils lacking both CXCR2 and CXCR4 displayed constitutive mobilization, showing that CXCR4 plays a dominant role in neutrophil trafficking. With regard to CXCR2 ligands, bone marrow endothelial cells and osteoblasts constitutively expressed the ELR+ chemokines CXCL1 and CXCL2, and CXCL2 expression was induced in endothelial cells during G-CSF–induced neutrophil mobilization. Collectively, these data suggest that CXCR2 signaling is a second chemokine axis that interacts antagonistically with CXCR4 to regulate neutrophil release from the bone marrow.
Kyle J. Eash, Adam M. Greenbaum, Priya K. Gopalan, Daniel C. Link
Mutations in the tumor-suppressor gene phosphatase and tensin homolog deleted on chromosome 10 (Pten) are associated with multiple cancers in humans, including T cell malignancies. Targeted deletion of Pten in T cells induces both a disseminated “mature phenotype” lymphoma and a lymphoproliferative autoimmune syndrome in mice. Here, we have shown that these two diseases are separable and mediated by T lineage cells of distinct developmental stages. Loss of PTEN was found to be a powerful driver of lymphomagenesis within the thymus characterized by overexpression of the c-myc oncogene. In an otherwise normal thymic environment, PTEN-deficient T cell lymphomas invariably harbored RAG-dependent reciprocal t(14:15) chromosomal translocations involving the T cell receptor alpha/delta locus and c-myc, and their survival and growth was TCR dependent, but Notch independent. However, lymphomas occurred even if TCR recombination was prevented, although these lymphomas were less mature, arose later in life, and, importantly, were dependent upon Notch pathways to upregulate c-myc expression. In contrast, using the complementary methods of early thymectomy and adoptive transfers, we found that PTEN-deficient mature T cells were unable to undergo malignant transformation but were sufficient for the development of autoimmunity. These data suggest multiple and distinct regulatory roles for PTEN in the molecular pathogenesis of lymphoma and autoimmunity.
Xiaohe Liu, Jodi L. Karnell, Bu Yin, Ruan Zhang, Jidong Zhang, Peiying Li, Yongwon Choi, Jonathan S. Maltzman, Warren S. Pear, Craig H. Bassing, Laurence A. Turka
Establishing long-term allograft acceptance without the requirement for continuous immunosuppression, a condition known as allograft tolerance, is a highly desirable therapeutic goal in solid organ transplantation. Determining which recipients would benefit from withdrawal or minimization of immunosuppression would be greatly facilitated by biomarkers predictive of tolerance. In this study, we identified the largest reported cohort to our knowledge of tolerant renal transplant recipients, as defined by stable graft function and receiving no immunosuppression for more than 1 year, and compared their gene expression profiles and peripheral blood lymphocyte subsets with those of subjects with stable graft function who are receiving immunosuppressive drugs as well as healthy controls. In addition to being associated with clinical and phenotypic parameters, renal allograft tolerance was strongly associated with a B cell signature using several assays. Tolerant subjects showed increased expression of multiple B cell differentiation genes, and a set of just 3 of these genes distinguished tolerant from nontolerant recipients in a unique test set of samples. This B cell signature was associated with upregulation of CD20 mRNA in urine sediment cells and elevated numbers of peripheral blood naive and transitional B cells in tolerant participants compared with those receiving immunosuppression. These results point to a critical role for B cells in regulating alloimmunity and provide a candidate set of genes for wider-scale screening of renal transplant recipients.
Kenneth A. Newell, Adam Asare, Allan D. Kirk, Trang D. Gisler, Kasia Bourcier, Manikkam Suthanthiran, William J. Burlingham, William H. Marks, Ignacio Sanz, Robert I. Lechler, Maria P. Hernandez-Fuentes, Laurence A. Turka, Vicki L. Seyfert-Margolis
The potent regulatory properties of NKT cells render this subset of lipid-specific T cells a promising target for immunotherapeutic interventions. The marine sponge glycolipid α-galactosylceramide (αGalCer) is the prototypic NKT cell agonist, which elicits this function when bound to CD1d. However, our understanding of the in vivo properties of NKT cell agonists and the host factors that control their bioactivity remains very limited. In this report, we isolated the enzyme fatty acid amide hydrolase (FAAH) from mouse serum as an αGalCer-binding protein that modulates the induction of key effector functions of NKT cells in vivo. FAAH bound αGalCer in vivo and in vitro and was required for the efficient targeting of lipid antigens for CD1d presentation. Immunization of Faah-deficient mice with αGalCer resulted in a reduced systemic cytokine production, but enhanced expansion of splenic NKT cells. This distinct NKT response conferred a drastically increased adjuvant effect and strongly promoted protective CTL responses. Thus, our findings identify not only the presence of FAAH in normal mouse serum, but also its critical role in the tuning of immune responses to lipid antigens by orchestrating their transport and targeting for NKT cell activation. Our results suggest that the serum transport of lipid antigens directly shapes the quality of NKT cell responses, which could potentially be modulated in support of novel vaccination strategies.
Stefan Freigang, Victoria Zadorozhny, Michele K. McKinney, Philippe Krebs, Rana Herro, Joanna Pawlak, Lisa Kain, Nicolas Schrantz, Kim Masuda, Yang Liu, Paul B. Savage, Albert Bendelac, Benjamin F. Cravatt, Luc Teyton
Clinical tools that measure changes in immune cell metabolism would improve the diagnosis and treatment of immune dysfunction. PET, utilizing probes for specific metabolic processes, detects regions of immune activation in vivo. In this study we investigated the immune cell specificity of PET probes for two different metabolic pathways: [18F]–2-fluorodeoxyglucose ([18F]-FDG) for glycolysis and [18F]–2-fluoro-d-(arabinofuranosyl)cytosine ([18F]-FAC) for deoxycytidine salvage. We isolated innate and adaptive immune cells from tissues of mice challenged with a retrovirus-induced sarcoma and measured their ability to accumulate FDG and FAC. We determined that the two probes had distinct patterns of accumulation: FDG accumulated to the highest levels in innate immune cells, while FAC accumulated predominantly in CD8+ T cells in a manner that correlated with cellular proliferation. This study demonstrates that innate and adaptive cell types differ in glycolytic and deoxycytidine salvage demands during an immune response and that these differential metabolic requirements can be detected with specific PET probes. Our findings have implications for the interpretation of clinical PET scans that use [18F]-FDG or [18F]-FAC to assess immune function in vivo and suggest potential applications of metabolic PET to monitor the effects of targeted immune modulation.
Evan Nair-Gill, Stephanie M. Wiltzius, Xiao X. Wei, Donghui Cheng, Mireille Riedinger, Caius G. Radu, Owen N. Witte
IgE-mediated hypersensitivity is central to the pathogenesis of asthma and other allergic diseases. Although neutralization of serum IgE with IgE-specific antibodies is in general an efficacious treatment for allergic asthma, one limitation of this approach is its lack of effect on IgE production. Here, we have developed a strategy to disrupt IgE production by generating monoclonal antibodies that target a segment of membrane IgE on human IgE-switched B cells that is not present in serum IgE. This segment is known as the M1′ domain, and using genetically modified mice that contain the human M1′ domain inserted into the mouse IgE locus, we demonstrated that M1′-specific antibodies reduced serum IgE and IgE-producing plasma cells in vivo, without affecting other immunoglobulin isotypes. M1′-specific antibodies were effective when delivered prophylactically and therapeutically in mouse models of immunization, allergic asthma, and Nippostrongylus brasiliensis infection, likely by inducing apoptosis of IgE-producing B cells. In addition, we generated a humanized M1′-specific antibody that was active on primary human cells in vivo, as determined by its reduction of serum IgE levels and IgE plasma cell numbers in a human PBMC-SCID mouse model. Thus, targeting of human IgE-producing B cells with apoptosis-inducing M1′-specific antibodies may be a novel treatment for asthma and allergy.
Hans D. Brightbill, Surinder Jeet, Zhonghua Lin, Donghong Yan, Meijuan Zhou, Martha Tan, Allen Nguyen, Sherry Yeh, Donnie Delarosa, Steven R. Leong, Terence Wong, Yvonne Chen, Mark Ultsch, Elizabeth Luis, Sree Ranjani Ramani, Janet Jackman, Lino Gonzalez, Mark S. Dennis, Anan Chuntharapai, Laura DeForge, Y. Gloria Meng, Min Xu, Charles Eigenbrot, Wyne P. Lee, Canio J. Refino, Mercedesz Balazs, Lawren C. Wu