Samia J. Khoury

The Tim-3 ligand galectin-9 negatively regulates T helper type 1 immunity

Tim-3 is a T helper type 1 (TH1)–specific cell surface molecule that seems to regulate TH1 responses and the induction of peripheral tolerance. However, the identity of the Tim-3 ligand and the mechanism by which this ligand inhibits the function of effector TH1 cells remain unknown. Here we show that galectin-9 is the Tim-3 ligand. Galectin-9-induced intracellular calcium flux, aggregation and death of TH1 cells were Tim-3-dependent in vitro, and administration of galectin-9 in vivo resulted in selective loss of interferon-γ-producing cells and suppression of TH1 autoimmunity. These data suggest that the Tim-3–galectin-9 pathway may have evolved to ensure effective termination of effector TH1 cells.

Directed migration of neural stem cells to sites of CNS injury by the stromal cell-derived factor 1α/CXC chemokine receptor 4 pathway

Migration toward pathology is the first critical step in stem cell engagement during regeneration. Neural stem cells (NSCs) migrate through the parenchyma along nonstereotypical routes in a precise directed manner across great distances to injury sites in the CNS, where they might engage niches harboring local transiently expressed reparative signals. The molecular mechanisms for NSC mobilization have not been identified. Because NSCs seem to home similarly to pathologic sites derived from disparate etiologies, we hypothesized that the inflammatory response itself, a characteristic common to all, guides the behavior of potentially reparative cells. As proof of concept, we show that human NSCs migrate in vivo (including from the contralateral hemisphere) toward an infarcted area (a representative CNS injury), where local astrocytes and endothelium up-regulate the inflammatory chemoattractant stromal cell-derived factor 1α (SDF-1α). NSCs express CXC chemokine receptor 4 (CXCR4), the cognate receptor for SDF-1α. Exposure of SDF-1α to quiescent NSCs enhances proliferation, promotes chain migration and transmigration, and activates intracellular molecular pathways mediating engagement. CXCR4 blockade abrogates their pathology-directed chain migration, a developmentally relevant mode of tangential migration that, if recapitulated, could explain homing along nonstereotypical paths. Our data implicate SDF-1α/CXCR4, representative of the inflammatory milieu characterizing many pathologies, as a pathway that activates NSC molecular programs during injury and suggest that inflammation may be viewed not simply as playing an adverse role but also as providing stimuli that recruit cells with a regenerative homeostasis-promoting capacity. CXCR4 expression within germinal zones suggests that NSC homing after injury and migration during development may invoke similar mechanisms.

Fourth international consultation on incontinence recommendations of the international scientific committee: Evaluation and treatment of urinary incontinence, pelvic organ prolapse, and fecal incontinence†‡§¶‖

P. Abrams , K.E. Andersson, L. Birder, L. Brubaker, L. Cardozo, C. Chapple, A. Cottenden, W. Davila, D. de Ridder, R. Dmochowski, M. Drake, C. DuBeau, C. Fry, P. Hanno, J. Hay Smith, S. Herschorn, G. Hosker, C. Kelleher, H. Koelbl, S. Khoury,* R. Madoff, I. Milsom, K. Moore, D. Newman, V. Nitti, C. Norton, I. Nygaard, C. Payne, A. Smith, D. Staskin, S. Tekgul, J. Thuroff, A. Tubaro, D. Vodusek, A. Wein, and J.J. Wyndaele and the Members of the Committees

IL-4 inhibits TGF-beta-induced Foxp3+ T cells and, together with TGF-beta, generates IL-9+ IL-10+ Foxp3(-) effector T cells.

Transcription factor Foxp3 is critical for generating regulatory T cells (Treg cells). Transforming growth factor-β (TGF-β) induces Foxp3 and suppressive Treg cells from naive T cells, whereas interleukin 6 (IL-6) inhibits the generation of inducible Treg cells. Here we show that IL-4 blocked the generation of TGF-β-induced Foxp3+ Treg cells and instead induced a population of T helper cells that produced IL-9 and IL-10. The IL-9+IL-10+ T cells demonstrated no regulatory properties despite producing abundant IL-10. Adoptive transfer of IL-9+IL-10+ T cells into recombination-activating gene 1–deficient mice induced colitis and peripheral neuritis, the severity of which was aggravated if the IL-9+IL-10+ T cells were transferred with CD45RBhi CD4+ effector T cells. Thus IL-9+IL-10+ T cells lack suppressive function and constitute a distinct population of helper-effector T cells that promote tissue inflammation.

The Programmed Death-1 (PD-1) Pathway Regulates Autoimmune Diabetes in Nonobese Diabetic (NOD) Mice

Programmed death-1 (PD-1) receptor, an inhibitory costimulatory molecule found on activated T cells, has been demonstrated to play a role in the regulation of immune responses and peripheral tolerance. We investigated the role of this pathway in the development of autoimmune diabetes. PD-1 or PD-L1 but not PD-L2 blockade rapidly precipitated diabetes in prediabetic female nonobese diabetic (NOD) mice regardless of age (from 1 to 10-wk-old), although it was most pronounced in the older mice. By contrast, cytotoxic T lymphocyte–associated antigen 4 (CTLA-4) blockade induced disease only in neonates. Male NOD mice also developed diabetes after PD-1–PD-L1 pathway blockade, but NOR mice, congenic to NOD but resistant to the development of diabetes, did not. Insulitis scores were significantly higher and frequency of interferon γ–producing GAD-reactive splenocytes was increased after PD-1–PD-L1 pathway blockade compared with controls. Interestingly, PD-L1 but not PD-L2 was found to be expressed on inflamed islets of NOD mice. These data demonstrate a central role for PD-1–PD-L1 interaction in the regulation of induction and progression of autoimmune diabetes in the NOD mouse and provide the rationale to develop new therapies to target this costimulatory pathway in this disease.

Induction of circulating myelin basic protein and proteolipid protein-specific transforming growth factor-beta1-secreting Th3 T cells by oral administration of myelin in multiple sclerosis patients.

Oral administration of antigen is a long recognized method of inducing systemic immune tolerance. In animals with experimental autoimmune disease, a major mechanism of oral tolerance triggered by oral administration of antigen involves the induction of regulatory T cells that mediate active suppression by secreting the cytokine TGF-beta 1. Multiple sclerosis (MS) is a presumed T cell-mediated Th1 type autoimmune disease. Here, we investigated whether in MS patients oral myelin treatment, containing both myelin basic protein (MBP) and proteolipid protein (PLP), induced antigen specific MBP or PLP reactive T cells that either secreted IL4, TGF-beta1, or alternatively did Th1 type sensitization occur as measured by IFN-gamma secretion. Specifically, 4,860 short-term T cell lines were generated to either MBP, PLP, or tetanus toxoid (TT) from 34 relapsing-remitting MS patients: 17 orally treated with bovine myelin daily for a minimum of 2 yr as compared to 17 nontreated patients. We found a marked increase in the relative frequencies of both MBP and PLP specific TGF-beta1-secreting T cell lines in the myelin treated MS patients as compared to non-treated MS patients (MBP P < 0.001, PLP P < 0.003). In contrast, no change in the frequency of MBP or PLP specific IFN-gamma or TT specific TGF-beta1 secreting T cells were observed. These results suggest that the oral administration of antigens generates antigen specific TGF-beta1 secreting Th3 cells of presumed mucosal origin that represent a distinct lineage of T cells. Since antigen-specific TGF-beta1 secreting cells localize to the target organ and then suppress inflammation in the local microenvironment, oral tolerization with self antigens may provide a therapeutic approach for the treatment of cell-mediated autoimmune disease which does not depend upon knowledge of the antigen specificity of the original T cell clone triggering the autoimmune cascade.

Expression of Cux-1 and Cux-2 in the subventricular zone and upper layers II-IV of the cerebral cortex.

Little is known about how neurons in the different layers of the mammalian cerebral cortex are specified at the molecular level. Expression of two homologues of the Drosophila homeobox Cut gene, Cux‐1 and Cux‐2, is strikingly specific to the pyramidal neurons of the upper layers (II–IV) of the murine cortex, suggesting that they may define the molecular identity of these neurons. An antibody against Cux‐1 labels the nucleus of most of the postmitotic upper layer neurons but does not label parvoalbumin‐positive cortical interneurons that derive from the medial ganglionic eminence. Cux‐1 and Cux‐2 represent early markers of neuronal differentiation; both genes are expressed in postmitotic cortical neurons from embryonic stages to adulthood and in the proliferative regions of the developing cortex. In precursors cells, Cux‐1 immunoreactivity is weak and diffuse in the cytoplasm and nucleus of ventricular zone (VZ) cells, whereas it is nuclear in the majority of bromodeoxyuridine (BrdU)‐positive subventricular zone (SVZ) dividing cells, suggesting that Cux‐1 function is first activated in SVZ cells. Cux‐2 mRNA expression is also found in the embryonic SVZ, overlapping with BrdU‐positive dividing precursors, but it is not expressed in the VZ. A null mutation in Pax‐6 disrupts Cux‐2 expression in the SVZ and Cux‐1 and Cux‐2 expression in the postmigratory cortical neurons. Thus, these data support the existence of an intermediate neuronal precursor in the SVZ dedicated to the generation of upper layer neurons, marked specifically by Cux‐2. The patterns of expression of Cux genes suggest potential roles as determinants of the neuronal fate of the upper cortical layer neurons. J. Comp. Neurol. 479:168–180, 2004.

Critical Role of the Programmed Death-1 (PD-1) Pathway in Regulation of Experimental Autoimmune Encephalomyelitis

Experimental autoimmune encephalomyelitis (EAE) is mediated by autoantigen-specific T cells dependent on critical costimulatory signals for their full activation and regulation. We report that the programmed death-1 (PD-1) costimulatory pathway plays a critical role in regulating peripheral tolerance in murine EAE and appears to be a major contributor to the resistance of disease induction in CD28-deficient mice. After immunization with myelin oligodendrocyte glycoprotein (MOG) there was a progressive increase in expression of PD-1 and its ligand PD-L1 but not PD-L2 within the central nervous system (CNS) of mice with EAE, peaking after 3 wk. In both wild-type (WT) and CD28-deficient mice, PD-1 blockade resulted in accelerated and more severe disease with increased CNS lymphocyte infiltration. Worsening of disease after PD-1 blockade was associated with a heightened autoimmune response to MOG, manifested by increased frequency of interferon γ–producing T cells, increased delayed-type hypersensitivity responses, and higher serum levels of anti-MOG antibody. In vivo blockade of PD-1 resulted in increased antigen-specific T cell expansion, activation, and cytokine production. Interestingly, PD-L2 but not PD-L1 blockade in WT animals also resulted in disease augmentation. Our data are the first demonstration that the PD-1 pathway plays a critical role in regulating EAE.

CD11b+Ly-6Chi Suppressive Monocytes in Experimental Autoimmune Encephalomyelitis

Innate immune cells may regulate adaptive immunity by balancing different lineages of T cells and providing negative costimulation. In addition, CD11b+Gr-1+ myeloid-derived suppressor cells have been described in tumor, parasite infection, and severe trauma models. In this study, we observe that splenic CD11b+ cells markedly increase after experimental autoimmune encephalomyelitis (EAE) immunization, and they suppress T cell proliferation in vitro. Although >80% of CD11b+ cells express varying levels of Gr-1, only a small population of CD11b+Ly-6Chigh inflammatory monocytes (IMC) can efficiently suppress T cell proliferation and induce T cell apoptosis through the production of NO. IFN-γ produced by activated T cells is essential to induce IMC suppressive function. EAE immunization increases the frequencies of IMC in the bone marrow, spleen, and blood, but not in the lymph nodes. At the peak of EAE, IMC represent ∼30% of inflammatory cells in the CNS. IMC express F4/80 and CD93 but not CD31, suggesting that they are immature monocytes. Furthermore, IMC have the plasticity to up-regulate NO synthase 2 or arginase 1 expression upon different cytokine treatments. These findings indicate that CD11b+Ly-6Chigh IMC induced during EAE priming are powerful suppressors of activated T cells. Further understanding of suppressive monocytes in autoimmune disease models may have important clinical implications for human autoimmune diseases.

A critical role for the programmed death ligand 1 in fetomaternal tolerance.

Fetal survival during gestation implies that tolerance mechanisms suppress the maternal immune response to paternally inherited alloantigens. Here we show that the inhibitory T cell costimulatory molecule, programmed death ligand 1 (PDL1), has an important role in conferring fetomaternal tolerance in an allogeneic pregnancy model. Blockade of PDL1 signaling during murine pregnancy resulted in increased rejection rates of allogeneic concepti but not syngeneic concepti. Fetal rejection was T cell– but not B cell–dependent because PDL1-specific antibody treatment caused fetal rejection in B cell–deficient but not in RAG-1–deficient females. Blockade of PDL1 also resulted in a significant increase in the frequency of IFN-γ–producing lymphocytes in response to alloantigen in an ELISPOT assay and higher IFN-γ levels in placental homogenates by ELISA. Finally, PDL1-deficient females exhibited decreased allogeneic fetal survival rates as compared with littermate and heterozygote controls and showed evidence of expansion of T helper type 1 immune responses in vivo. These results provide the first evidence that PDL1 is involved in fetomaternal tolerance.