Mitf is required for T cell maturation by regulating dendritic cell homing to the thymus.

Thymic dendritic cells (DCs) promote immune tolerance by regulating negative selection of autoreactive T cells in the thymus. How DC homing to the thymus is transcriptionally regulated is still unclear. Microphthalmia-associated transcription factor (Mitf) is broadly expressed and plays essential roles in the hematopoietic system. Here, we used Mitf-mutated mice (Mitfvit/vit) and found enlargement of the thymus and expansion of CD4/CD8 double-positive T cells. Mitf was highly expressed in a subset of thymic DCs among the hematopoietic system. Genetic mutation or pharmacological inhibition of Mitf in DCs decreased the expression levels of Itga4, which are critical molecules for the homing of DCs to the thymus. Further, inhibition of Mitf decreased thymic DC number. These results suggest a pivotal role of Mitf in the maintenance of T cell differentiation by regulating the homing of DC subsets within the thymus.

CD49d marks Th1 and Tfh-like antigen-specific CD4+ T cells during Plasmodium chabaudi infection.

Upon activation, specific CD4+ T cells up-regulate the expression of CD11a and CD49d, surrogate markers of pathogen-specific CD4+ T cells. However, using T-cell receptor transgenic mice specific for a Plasmodium antigen, termed PbT-II, we found that activated CD4+ T cells develop not only to CD11ahiCD49dhi cells, but also to CD11ahiCD49dlo cells during acute Plasmodium infection. CD49dhi PbT-II cells, localized in the red pulp of spleens, expressed transcription factor T-bet and produced IFN-γ, indicating that they were type 1 helper T (Th1)-type cells. In contrast, CD49dlo PbT-II cells resided in the white pulp/marginal zones and were a heterogeneous population, with approximately half of them expressing CXCR5 and a third expressing Bcl-6, a master regulator of follicular helper T (Tfh) cells. In adoptive transfer experiments, both CD49dhi and CD49dlo PbT-II cells differentiated into CD49dhi Th1-type cells after stimulation with antigen-pulsed dendritic cells, while CD49dhi and CD49dlo phenotypes were generally maintained in mice infected with Plasmodium chabaudi. These results suggest that CD49d is expressed on Th1-type Plasmodium-specific CD4+ T cells, which are localized in the red pulp of the spleen, and can be used as a marker of antigen-specific Th1 CD4+ T cells, rather than that of all pathogen-specific CD4+ T cells.

Dendritic Cell Accumulation in the Gut and Central Nervous System Is Differentially Dependent on α4 Integrins.

Homing of pathogenic CD4+ T cells to the CNS is dependent on α4 integrins. However, it is uncertain whether α4 integrins are also required for the migration of dendritic cell (DC) subsets, which sample Ags from nonlymphoid tissues to present it to T cells. In this study, after genetic ablation of Itga4 in DCs and monocytes in mice via the promoters of Cd11c and Lyz2 (also known as LysM), respectively, the recruitment of α4 integrin-deficient conventional and plasmacytoid DCs to the CNS was unaffected, whereas α4 integrin-deficient, monocyte-derived DCs accumulated less efficiently in the CNS during experimental autoimmune encephalomyelitis in a competitive setting than their wild-type counterparts. In a noncompetitive setting, α4 integrin deficiency on monocyte-derived DCs was fully compensated. In contrast, in small intestine and colon, the fraction of α4 integrin-deficient CD11b+CD103+ DCs was selectively reduced in steady-state. Yet, T cell-mediated inflammation and host defense against Citrobacter rodentium were not impaired in the absence of α4 integrins on DCs. Thus, inflammatory conditions can promote an environment that is indifferent to α4 integrin expression by DCs.

CD49d/CD29-integrin controls the accumulation of plasmacytoid dendritic cells into the CNS during neuroinflammation.

Plasmacytoid dendritic cells (pDCs) are found in the CNS during neuroinflammation and have been reported to exert regulatory functions in multiple sclerosis (MS) and its animal model experimental autoimmune encephalomyelitis (EAE). However, the mechanisms of entry of pDCs into the CNS as well as their phenotype and innate functional properties, once recruited into the CNS, have not been thoroughly examined. Herein, we show that pDCs rapidly accumulate into the brain and spinal cord during the acute phase of EAE, and maintain the expression of numerous phenotypic markers typical of peripheral pDCs. Functionally, CNS-pDCs constitutively expressed IRF7 and were able to rapidly produce type I IFNs and IL-12p40 upon ex vivo TLR-9 stimulation. Using adoptive transfer experiments, we provide evidence that CNS-pDC are recruited from the blood and accumulate into the CNS during the acute phase of EAE. Accumulation of pDCs into the CNS was strongly inhibited in the absence of CD29, but not CD18, suggesting a major role for ß1 but not ß2 integrins. Indeed, blocking the CD49d α4-integrins during acute EAE drastically diminished CNS-pDC numbers. Together, our results demonstrate that circulating pDCs are actively recruited into the CNS during acute EAE through a mechanism largely dependent on CD49d/CD29-integrins.

α4ß7+ CD4+ Effector/Effector Memory T Cells Differentiate into Productively and Latently Infected Central Memory T Cells by Transforming Growth Factor ß1 during HIV-1 Infection.

HIV-1 transmission occurs mainly through mucosal tissues. During mucosal transmission, HIV-1 preferentially infects α4ß7+ gut-homing CCR7- CD4+ effector/effector memory T cells (TEM) and results in massive depletion of these cells and other subsets of TEM in gut-associated lymphoid tissues. However, besides being eliminated by HIV-1, the role of TEM during the early stage of infection remains inconclusive. Here, using in vitro-induced α4ß7+ gut-homing TEM (α4ß7+ TEM), we found that α4ß7+ TEM differentiated into CCR7+ CD4+ central memory T cells (TCM). This differentiation was HIV-1 independent but was inhibited by SB431542, a specific transforming growth factor ß (TGF-ß) receptor I kinase inhibitor. Consistently, TEM-to-TCM differentiation was observed in α4ß7+ TEM stimulated with TGF-ß1 (TGF-ß). The TCM properties of the TGF-ß-induced TEM-derived TCM (α4ß7+ TCM) were confirmed by their enhanced CCL19 chemotaxis and the downregulation of surface CCR7 upon T cell activation in vitro Importantly, the effect of TGF-ß on TCM differentiation also held in TEM directly isolated from peripheral blood. To investigate the significance of the TGF-ß-dependent TEM-to-TCM differentiation in HIV/AIDS pathogenesis, we observed that both productively and latently infected α4ß7+ TCM could differentiate from α4ß7+ TEM in the presence of TGF-ß during HIV-1 infection. Collectively, this study not only provides a new insight for the plasticity of TEM but also suggests that the TGF-ß-dependent TEM-to-TCM differentiation is a previously unrecognized mechanism for the formation of latently infected TCM after HIV-1 infection.IMPORTANCE HIV-1 is the causative agent of HIV/AIDS, which has led to millions of deaths in the past 30 years. Although the implementation of highly active antiretroviral therapy has remarkably reduced the HIV-1-related morbidity and mortality, HIV-1 is not eradicated in treated patients due to the presence of latent reservoirs. Besides, the pathogenesis in CD4 T cells early after infection still remains elusive. Immediately after HIV-1 mucosal infection, CD4 T cells are preferentially infected and depleted. However, in addition to being depleted, the other roles of the CD4 T cells, especially the effector/effector memory T cells (TEM), in disease progression are not completely understood. The significance of this study is in revealing a novel mechanism for the formation of latently HIV-1-infected central memory CD4 T cells, a major latent reservoir from CD4 TEM after infection. Our findings suggest previously unrecognized roles of CD4 TEM in HIV-1 pathogenesis.

Optimization of Receptor Occupancy Assays in Mass Cytometry: Standardization Across Channels with QSC Beads.

Receptor occupancy, the ratio between amount of drug bound and amount of total receptor on single cells, is a biomarker for treatment response to therapeutic monoclonal antibodies. Receptor occupancy is traditionally measured by flow cytometry. However, spectral overlap in flow cytometry limits the number of markers that can be measured simultaneously. This restricts receptor occupancy assays to the analysis of major cell types, although rare cell populations are of potential therapeutic relevance. We therefore developed a receptor occupancy assay suitable for mass cytometry. Measuring more markers than currently available in flow cytometry allows simultaneous receptor occupancy assessment and high-parameter immune phenotyping in whole blood, which should yield new insights into disease activity and therapeutic effects. However, varying sensitivity across the mass cytometer detection range may lead to misinterpretation of the receptor occupancy when drug and receptor are detected in different channels. In this report, we describe a method for optimization of mass cytometry receptor occupancy measurements by using antibody-binding quantum simply cellular (QSC) beads for standardization across channels with different sensitivities. We evaluated the method in a mass cytometry-based receptor occupancy assay for natalizumab, a therapeutic antibody used in multiple sclerosis treatment that binds to α4-integrin, which is expressed on leukocyte cell surfaces. Peripheral blood leukocytes from a treated patient were stained with a panel containing metal-conjugated antibodies for detection of natalizumab and α4-integrin. QSC beads with known antibody binding capacity were stained with the same metal-conjugated antibodies and were used to standardize the signal intensity in the leukocyte sample before calculating receptor occupancy. We found that QSC bead standardization across channels corrected for sensitivity differences for detection of drug and receptor and generated more accurate results than observed without standardization. © 2019 The Authors. Cytometry Part A published by Wiley Periodicals, Inc. on behalf of International Society for Advancement of Cytometry.

Natalizumab for Multiple Sclerosis: A Case in Point for the Impact of Translational Neuroimmunology.

Advances in translational neuroimmunology over the last two decades have revolutionized the treatment of relapsing forms of multiple sclerosis. A pathological hallmark of multiple sclerosis is the presence of leukocytes in the areas of disease activity in the CNS. Natalizumab inhibits the trafficking of lymphocytes from the blood into the brain and spinal cord by blocking the adhesion molecule α4-integrin. Representing the enormous success of a molecular targeted approach, natalizumab was the first mAb approved for the treatment of relapsing-remitting multiple sclerosis. However, only a few months after its approval, natalizumab was withdrawn from the market because of an unanticipated life threatening adverse effect: progressive multifocal leukoencephalopathy. Natalizumab was later reintroduced with required adherence to a strict monitoring program. In this article, we review the bench-to-bedside journey of natalizumab, along with the lessons learned from postmarketing studies.

Cysteinyl leukotriene receptor 1 expression identifies a subset of neutrophils during the antiviral response that contributes to postviral atopic airway disease.

BACKGROUND: Viral respiratory tract infections increase the risk of development and exacerbation of atopic disease. Previously, we demonstrated the requirement for a neutrophil (PMN) subset expressing CD49d to drive development of postviral atopic airway disease in mice. OBJECTIVE: We sought to determine whether human CD49d+ PMNs are present in the nasal mucosa during acute viral respiratory tract infections and further characterize this PMN subset in human subjects and mice. METHODS: Sixty subjects (5-50 years old) were enrolled within 4 days of acute onset of upper respiratory symptoms. Nasal lavage for flow cytometry and nasal swabs for viral PCR were performed at enrollment and during convalescence. The Sendai virus mouse model was used to investigate the phenotype and functional relevance of CD49d+ PMNs. RESULTS: CD49d+ PMN frequency was significantly higher in nasal lavage fluid during acute respiratory symptoms in all subjects (2.9% vs 1.0%, n = 42, P < .001). In mice CD49d+ PMNs represented a "proatopic" neutrophil subset that expressed cysteinyl leukotriene receptor 1 (CysLTR1) and produced TNF, CCL2, and CCL5. Inhibition of CysLTR1 signaling in the first days of a viral respiratory tract infection was sufficient to reduce accumulation of CD49d+ PMNs in the lungs and development of postviral atopic airway disease. Similar to the mouse, human CD49d+ PMNs isolated from nasal lavage fluid during a viral respiratory tract infection expressed CysLTR1. CONCLUSION: CD49d and CysLTR1-coexpressing PMNs are present during symptoms of an acute viral respiratory tract infection in human subjects. Further study is needed to examine selective targeting of proatopic neutrophils as a potential therapeutic strategy to prevent development of postviral atopic airway disease.

In vivo neutralization of α4 and ß7 integrins inhibits eosinophil trafficking and prevents lung injury during tropical pulmonary eosinophilia in mice.

Integrins regulate leukocyte trafficking during homeostasis and inflammatory conditions. However, the role of α4 and ß7 integrins in guiding eosinophil transmigration into the lungs during filarial manifestation of Tropical Pulmonary Eosinophilia (TPE) has not been explored. In this study, mice exhibiting TPE manifestations were administered with in vivo neutralizing antibodies against integrins α4 and ß7 or their combination and immuno-pathological parameters were evaluated. Results show an intact lung barrier, significantly lower lung inflammation and reduced eosinophil counts in the Bronchoalveolar lavage fluid and lungs of mice receiving anti-α4+ ß7 treatment. Reduced eosinophil peroxidase and ß-hexosaminidase activity, downregulation of inflammatory genes, lower production of inflammatory lipid intermediates like prostaglandins E2 and D2, leukotriene B4 and cysteinyl leukotrienes were also noted in anti-α4+ ß7 treated mice. Reduced accumulation of central memory, effector memory, regulatory T cells and lower production of IL-4, IL-5, and TGF-ß were other cardinal features of anti-α4+ ß7 treated mice lungs. Flow cytometry-sorted lung eosinophils from anti-α4+ ß7 treated mice showed higher apoptotic potential, downregulated anti-apoptotic gene Bcl-2, and exhibited reduced F-actin polymerization and calcium influx as compared to IgG controls. In summary, neutralization of α4+ ß7 integrins impairs the transmigration, activation and survival of eosinophils and reduces TPE induced pathology in mice lungs.

Cutting Edge: Integrin α4 Is Required for Regulatory B Cell Control of Experimental Autoimmune Encephalomyelitis.

The neutralization of integrin α4 (Itga4) is currently used as treatment in multiple sclerosis. Although most studies have focused on its function on lymphocyte migration to the CNS, we have uncovered the importance of Itga4 for the generation of regulatory B cells in peripheral immune organs and their control of pathogenic T cell response and CNS pathology. Our study underscores the importance of looking at the dual role of B cells in CNS autoimmunity and provides important perspectives regarding the efficacy and side effects associated with Itga4 neutralization and other B cell-targeting therapies.

The role of α4 integrin in Theiler's murine encephalomyelitis virus (TMEV)-induced demyelinating disease: an infectious animal model for multiple sclerosis (MS).

Natalizumab, which is an antibody against α4 integrin, has been used for the treatment of multiple sclerosis. In the present study, we investigated both the role of α4 integrin and the therapeutic effect of HCA3551, a newly synthesized orally active small molecule α4 integrin antagonist, in the development of Theiler's murine encephalomyelitis virus-induced demyelinating disease (TMEV-IDD). The mRNA levels of α4 integrins were significantly up-regulated in the central nervous system (CNS) of mice with TMEV-IDD as compared with naive mice (*P < 0.05). HCA3551 treatment in the effector phase significantly suppressed both the clinical and histological development of TMEV-IDD. The number of infiltrating mononuclear inflammatory cells in the CNS was significantly decreased in the mice treated with HCA3551 (**P < 0.01). The labeling indices for CD68 antigen and the absolute cell numbers of TNF-α-producing CD4+ T cells and IFN-γ-producing CD8+ T cells were significantly decreased in the CNS of mice treated with HCA3551 (*P < 0.05). HCA3551 treatment in the effector phase might inhibit the binding of α4 integrin to vascular cell adhesion molecule-1, thereby decreasing the number of mononuclear cells in the CNS.

Expansion of CD11b+Ly6Ghigh and CD11b+CD49d+ myeloid cells with suppressive potential in mice with chronic inflammation and light-at-night-induced circadian disruption.

OBJECTIVE: Myeloid-derived suppressor cells (MDSCs) are important negative regulators of immune processes in cancer and other pathological conditions. We suggested that MDSCs play a key role in pathogenesis of chronic inflammation, which precedes and, to a certain extent, induces carcinogenesis. The present study aimed at investigation of MDSCs arising during chronic inflammation and light-at-night (LN)-induced stress, which is shown to accelerate chronic diseases. SUBJECTS: 67 CD-1 mice and in vitro MDSC cultures. TREATMENT: Adjuvant arthritis was induced by a subdermal injection of complete Freund's adjuvant. LN was induced by illumination of 750 lx at night. METHODS: Flow cytometry for evaluation of cell phenotypes and MTT standard test for cell proliferation were used. RESULTS: Increased levels of splenic CD11b+Ly6Ghigh and CD11b+CD49d+ myeloid cells possessing suppressive potential in mice with adjuvant arthritis are shown. LN amplifies the process of CD11b+Ly6Ghigh expansion in mice with adjuvant arthritis. Expression of CD62L and CD195 is elevated on the myeloid cells during exposure to LN. CONCLUSIONS: Our study raises the possibility that CD11b+Ly6Ghigh and CD11b+CD49d+ MDSCs play an important role in the induction of immunosuppressive environment typical for chronic inflammation. Also, LN can affect immune responses during chronic inflammation through recruitment of MDSCs from the bone marrow.

Early Development in the Peritoneal Cavity of CD49dhigh Th1 Memory Phenotype CD4+ T Cells with Enhanced B Cell Helper Activity.

The Th cells that regulate peritoneal B-1 cell functions have not yet been well characterized. To address this question, we investigated peritoneal CD4(+) T cells, observed a high frequency of the conjugates of B-CD4(+) T cells in the peritoneal cavity, and identified a population of CD49d(high)CD4(+) T cells that constituted about half of all CD4(+) T cells in the peritoneal cavity, but were rarely found in other compartments. Peritoneal CD49d(high)CD4(+) T cells were CD44(high)CD62L(low); expressed integrin α4ß1 and CXCR3; and rapidly secreted IFN-γ, TNF-α, and IL-2, showing features of proinflammatory Th1 cells. Peritoneal CD49d(high)CD4(+) T cells developed spontaneously, were detected at the age of 12 d, and showed stem cell-like properties. Their development was observed in mice deficient for signaling lymphocytic activation molecule-associated protein, but not in athymic nude mice and mice lacking in expression of MHC class II on thymic epithelial cells. Peritoneal CD49d(high)CD4(+) T cells were more resistant to irradiation and more sensitive to NAD-induced cell death than CD49d(low)CD4(+) T cells. Notably, peritoneal CD49d(high)CD4(+) T cells also showed some characteristics of follicular Th cells, such as the expression of programmed cell death 1, ICOS, IL-21, and CXCR5. Moreover, peritoneal CD49d(high)CD4(+) T cells enhanced the secretion of IgM Abs by B-1a cells and IgG Abs by splenic B cells. These data suggest that peritoneal CD49d(high)CD4(+) T cells may be innate-like CD4(+) T cells, which develop early and have a dual capacity to support both humoral and cellular immunity.

Anti-α4 antibody treatment blocks virus traffic to the brain and gut early, and stabilizes CNS injury late in infection.

Four SIV-infected monkeys with high plasma virus and CNS injury were treated with an anti-α4 blocking antibody (natalizumab) once a week for three weeks beginning on 28 days post-infection (late). Infection in the brain and gut were quantified, and neuronal injury in the CNS was assessed by MR spectroscopy, and compared to controls with AIDS and SIV encephalitis. Treatment resulted in stabilization of ongoing neuronal injury (NAA/Cr by 1H MRS), and decreased numbers of monocytes/macrophages and productive infection (SIV p28+, RNA+) in brain and gut. Antibody treatment of six SIV infected monkeys at the time of infection (early) for 3 weeks blocked monocyte/macrophage traffic and infection in the CNS, and significantly decreased leukocyte traffic and infection in the gut. SIV - RNA and p28 was absent in the CNS and the gut. SIV DNA was undetectable in brains of five of six early treated macaques, but proviral DNA in guts of treated and control animals was equivalent. Early treated animals had low-to-no plasma LPS and sCD163. These results support the notion that monocyte/macrophage traffic late in infection drives neuronal injury and maintains CNS viral reservoirs and lesions. Leukocyte traffic early in infection seeds the CNS with virus and contributes to productive infection in the gut. Leukocyte traffic early contributes to gut pathology, bacterial translocation, and activation of innate immunity.

Increased peripheral IL-4 leads to an expanded virtual memory CD8+ population.

Memory-phenotype CD8(+) T cells can arise even in the absence of overt Ag stimulation. Virtual memory (VM) CD8(+) T cells are CD8(+) T cells that develop a memory phenotype in the periphery of wild-type mice in an IL-15-dependent manner. Innate CD8(+) T cells, in contrast, are memory-phenotype CD8(+) T cells that develop in the thymus in response to elevated thymic IL-4. It is not clear whether VM cells and innate CD8(+) T cells represent two independent T cell lineages or whether they arise through similar processes. In this study, we use mice deficient in Nedd4-family interacting protein 1 to show that overproduction of IL-4 in the periphery leads to an expanded VM population. Nedd4-family interacting protein 1(-/-) CD4(+) T cells produce large amounts of IL-4 due to a defect in JunB degradation. This IL-4 induces a memory-like phenotype in peripheral CD8(+) T cells that includes elevated expression of CD44, CD122, and Eomesodermin and decreased expression of CD49d. Thus, our data show that excess peripheral IL-4 is sufficient to cause an increase in the VM population. Our results suggest that VM and innate CD8(+) T cells may be more similar than previously appreciated.

Natalizumab analogon therapy is effective in a B cell-dependent multiple sclerosis model.

AIMS: Natalizumab is a humanized monoclonal antibody specific for CD49d receptors of integrins. It inhibits the entry of inflammatory cells into the central nervous system and is approved for the treatment of relapsing-remitting multiple sclerosis (MS). Several lines of evidence indicate an involvement of B cells and plasma cells in MS pathogenesis. However, treatment with the natalizumab analogon PS/2 immunoglobulin G (IgG) has so far only been investigated in T cell-mediated animal models of MS. Due to the importance of B lineage cells in the pathogenesis of MS, the objective of the present study has thus been to analyse the effects of PS/2 IgG in a mouse model of MS with T and B cell cooperation (OSE mice). METHODS: OSE mice were treated with the natalizumab analogon PS/2 IgG either at disease onset or after peak of disease. Treatment was also performed with PS/2 F(ab')2 fragments. RESULTS: PS/2 IgG treatment improved the clinical outcome and decreased spinal cord demyelination and immune cell infiltration if given early in the disease course. Treatment increased blood leukocytes and resulted in a partial internalization of CD49d in T and B cells. The therapeutic effects of PS/2 IgG injections were independent of the Fc fragment as F(ab')2 injections were equally beneficial. In contrast, PS/2 IgG was not effective when given late in the disease course. CONCLUSIONS: Results indicate that natalizumab may also be beneficial in MS with B cell-driven immunopathogenesis.

Blocking of α4 integrin does not protect from acute ischemic stroke in mice.

BACKGROUND AND PURPOSE: T lymphocytes have recently been identified as key mediators of tissue damage in ischemic stroke. The interaction between very late antigen-4 (VLA-4) and vascular adhesion molecule-1 is crucial for the transvascular egress of T lymphocytes, and inhibition of this interaction by specific antibodies is a powerful strategy to combat autoimmune neuroinflammation. However, whether pharmacological blocking of T-lymphocyte trafficking is also protective during brain ischemia is still unclear. We investigated the efficacy of a monoclonal antibody directed against VLA-4 in mouse models of ischemic stroke. METHODS: Transient and permanent middle cerebral artery occlusion was induced in male C57Bl/6 mice. Animals treated with a monoclonal anti-CD49d antibody (300 µg) 24 hours before or 3 hours after the onset of cerebral ischemia and stroke outcome, including infarct size, functional status, and mortality, were assessed between day 1 and day 7. The numbers of immune cells invading the ischemic brain were determined by immunocytochemistry and flow cytometry. RESULTS: Blocking of VLA-4 significantly reduced the invasion of T lymphocytes and neutrophils on day 5 after middle cerebral artery occlusion and inhibited the upregulation of vascular adhesion molecule-1. However, the anti-CD49d antibody failed to influence stroke outcome positively irrespective of the model or the time point investigated. CONCLUSIONS: Pharmacological inhibition of the VLA-4/vascular adhesion molecule-1 axis in experimental stroke was ineffective in our hands. Our results cast doubt on the effectiveness of anti-CD49d as a stroke treatment. Further translational studies should be performed before testing anti-VLA-4 antibodies in patients with stroke.

Targeting cells in motion: migrating toward improved therapies.

The development of clinical therapeutics that interfere with the migration of leukocytes has revolutionized the treatment of multiple sclerosis and holds great promise for the treatment of a wide range of inflammatory diseases. As the molecules essential for the multi-step adhesion cascade that mediates cellular migration have been elucidated, the number of potential targets available to modulate leukocyte trafficking has increased exponentially. In this Viewpoint, we briefly review our current understanding of these mole-cular targets and how these targets vary by tissue and leukocyte subset with emphasis on T cells. We then describe the two currently approved therapeutics that target cell migration, natalizumab and fingolimod, and discuss how an improved understanding of their function could pave the way for the development of safer and more efficacious therapies for inflammatory and autoimmune diseases.

CD49d Treg cells with high suppressive capacity are remarkably less efficient on activated CD45RA- than on naive CD45RA+ Teff cells.

BACKGROUND: Impairment of regulatory T cells (Tregs) in common autoimmune diseases seems likely. However, the extent of Treg deficiency (number, function) or differential susceptibility of T effector cells (Teffs) to suppression is not completely understood. We hypothesize that even in healthy individuals both cell populations are heterogeneous and differ in their suppressive capability and their susceptibility to suppression. MATERIAL AND METHODS: Lymphocytes were enriched by MACS for CD4(+)CD25(+) Tregs or CD4(+)CD25(-) Teffs. After multicolour staining (anti-CD25, anti-CD127, anti-CD49d or anti-CD45RA) highly purified Treg and Teff subpopulations were collected by FACS. Functional capacity of Tregs or suppressive susceptibility of Teffs was analyzed in an in vitro assay. RESULTS: When CD4(+)CD25(high)CD127(-/low) CD49d(-) Tregs were tested on naive CD4(+)CD127(+)CD25(-)CD45RA(+) Teffs (93.8 %) suppression was almost complete, while the suppressive capacity of CD4(+)CD25(high)CD127(-/low) CD49d(+) Tregs was significantly less (71.8 %). Suppressive activity was low when CD4(+)CD25(high)CD127(-/low) CD49d(+) Tregs were analyzed on CD4(+)CD127(+)CD25(-)CD45RA(-) Teffs (48.7%). CONCLUSION: Although CD49d(+) Tregs are functional, the suppressive capacity is significantly lower compared to CD49d(-) Tregs. CD45RA(+) Teffs can be completely suppressed, while CD45RA(-) Teffs display relative resistance. Phenotypic and functional heterogeneity of Tregs as well as Teffs has to be considered when analyzing deficiencies in immune regulation.

Therapeutic advantage of anti-VAP-1 over anti-α4 integrin antibody in concanavalin a-induced hepatitis.

UNLABELLED: Hepatitis induced by concanavalin A (Con A) in mice is well known to be a T-lymphocyte-mediated injury. It has been reported that T helper (Th)1 and Th2 lymphocytes use α4 integrin and vascular adhesion protein (VAP)-1, respectively, to adhere within the hepatic sinusoids. Therefore, we investigated whether inhibition of these molecules ameliorates or worsens the Con A-induced hepatic injury in vivo. Vehicle or antibody to α4 integrin or VAP-1 was intravenously administered 30 minutes before Con A administration. In control mice Con A markedly increased the serum alanine aminotransferase (ALT) level in a dose-dependent manner, and induced a massive infiltration of CD3, particularly interleukin (IL)-4 producing CD4 T cells and liver injury. Both parameters were reduced by anti-VAP-1 antibody despite antibody only blocking the adhesion, not the amine oxidase activity of VAP-1. Both activities of VAP-1 were eliminated in VAP-1-deficient mice and both Con A-induced liver injury and CD4 T-cell infiltration were eradicated. In contrast to anti-VAP-1, anti-α4 integrin antibody reduced interferon-gamma (IFN-γ)-producing CD3 T cells but this worsened Con A hepatitis, suggesting inhibition of a suppressor cell. Con A induced the recruitment of CD49d(+) monocytic myeloid-derived suppressor cells (MDSCs) and regulatory T cells (Tregs) into the liver. Anti-α4 integrin dramatically blocked the influx of MDSCs but not Tregs. CONCLUSION: Our findings show that VAP-1 and α4 integrin have opposing effects in Con A-induced hepatic injury, which is associated with blocking the recruitment of CD4 lymphocytes and monocytic MDSCs, respectively. Moreover, these data provide the rationale for a potential therapeutic approach to target adhesion molecules in autoimmune hepatitis.