"Thinking without thinking" about natalizumab and PML.

The novel multiple sclerosis (MS) therapeutic natalizumab has taken neurologists and their MS patients on a roller-coaster ride: initial encouraging efficacy data led to expedited release in the United States, followed by suspension of dosing with the unexpected occurrence of progressive multifocal leukoencephalopathy (PML) in three clinical trial participants. The drug was re-released in 2006, in a restricted distribution format. Aside from PML, natalizumab treatment was not associated with opportunistic infections, suggesting the possibility that PML in these individuals was mechanism-based, and was not a consequence of generalized immunosuppression.

Isolation of murine microglial cells for RNA analysis or flow cytometry.

There is increasing interest in the isolation of adult microglia to study their functions at a morphological and molecular level during normal and neuroinflammatory conditions. Microglia have important roles in brain homeostasis, and in disease states they exert neuroprotective or neurodegenerative functions. To assay expression profiles or functions of microglia, we have developed a method to isolate microglial cells and infiltrating leukocytes from adult mouse brain.

Inflammatory cell migration into the central nervous system: a few new twists on an old tale.

Understanding the mechanisms of leukocyte trafficking into the brain might provide insights into how to modulate pathologic immune responses or enhance host protective mechanisms in neuroinflammatory diseases such as multiple sclerosis. This review summarized our knowledge about the sites for leukocyte entry into the central nervous system, highlighting the routes from blood into the perivascular space and brain parenchyma through the blood-brain barrier. We further discussed the multistep paradigm of leukocyte-endothelial interactions at the blood-brain barrier, focusing on the adhesion molecules and chemokines involved in leukocyte transmigration.

Inflammatory progressive multifocal leukoencephalopathy in human immunodeficiency virus-negative patients.

Objective: Inflammatory progressive multifocal leukoencephalopathy (iPML) with enhancing magnetic resonance imaging (MRI) lesions and leukocyte infiltration occurs in human immunodeficiency virus (HIV)-infected individuals after highly active antiretroviral therapy (HAART) treatment. MRI diagnostic criteria for PML suggest that iPML does not occur in HIV-negative individuals.

Methods: We studied pathologically proved PML (12 by biopsy, 9 with MRI, 32 at autopsy).

CCR5 expression on monocytes and T cells: modulation by transmigration across the blood-brain barrier in vitro.

Observational studies in multiple sclerosis (MS) demonstrated altered expression of chemokine receptors (CkRs) on comparable populations of mononuclear cells (e.g. CD4(+)/CD45RO(+) T-cells) in brain sections compared with blood.

Evidence for synaptic stripping by cortical microglia.

Recent studies have described significant demyelination and microglial activation in the cerebral cortex of brains from multiple sclerosis patients. To date, however, experimental models of cortical demyelination or cortical inflammation have not been extensively studied. In this report we describe focal cortical inflammation induced by stereotaxic injection of killed bacteria (BCG), followed 1 month later by subcutaneous injection of the same antigen, a protocol that overcomes the immune privilege of the cortex.

Chemokine receptors as biomarkers in multiple sclerosis.

Leukocyte infiltrates characterize tissue inflammation and are thought to be integral in the pathogenesis of multiple sclerosis (MS). This attribute underlines the importance of understanding mechanisms of leukocyte migration. Chemokines are secreted proteins which govern leukocyte trafficking into targeted organs.

A novel model of demyelinating encephalomyelitis induced by monocytes and dendritic cells.

Local inflammation may be a precipitating event in autoimmune processes. In this study, we demonstrate that regulated influx of monocytes and dendritic cells (DC) into the CNS causes an acute neurological syndrome that results in a demyelinating encephalomyelitis. Expansion of monocytes and DC by conditional expression of Flt3 ligand in animals expressing CCL2 in the CNS promoted parenchymal cell infiltration and ascending paralysis in 100% of the mice within 9 days of Flt3 ligand induction.

CC chemokine receptor 2 is protective against noise-induced hair cell death: studies in CX3CR1(+/GFP) mice.

Acoustic trauma was recently shown to induce an inflammatory response in the ear characterized by rapid entry of macrophages in the spiral ligament. The current study seeks to elucidate the mechanisms involved in summoning macrophages to the cochlear lateral wall and the role macrophages play in noise-induced injury or repair. CCL2 and its primary receptor, CCR2, are the most widely validated effectors of monocyte chemotaxis in vivo.

Chemokines, mononuclear cells and the nervous system: heaven (or hell) is in the details.

Chemokines and their receptors are essential elements in leukocyte trafficking during health and disease. There are three (or more) distinct routes of leukocyte entry into the central nervous system (CNS), and molecular mechanisms of physiological and neuroinflammatory leukocyte recruitment to the CNS are slowly coming into view. Migration of immune cells into cerebrospinal fluid supports CNS immunosurveillance.

A mighty mouse: building a better model of multiple sclerosis.

The 2 cardinal cell populations mediating adaptive immunity are T and B lymphocytes. These cells play important but poorly understood roles in the immunopathological demyelinating disease multiple sclerosis (MS) and in a widely used animal model of human MS known as EAE. In the current issue of the JCI, 2 research teams report their parallel studies of double-transgenic mice expressing T and B cell receptors that recognize the same myelin protein (see the related articles beginning on pages 2385 and 2393).

Interferon-gamma-inducible protein (IP)-10 mRNA stabilized by RNA-binding proteins in monocytes treated with S100b.

Chemokines mediate the recruitment and activation of blood monocyte/macrophages and lymphocytes to sites of inflammation. Expression of the chemokine IP-10 (interferon-gamma-inducible protein) has been documented in several inflammatory and autoimmune disorders including type 1 diabetes. However, the mechanism of its expression in monocytes or its functional role in diabetes is not known.

Alterations in the oligodendrocyte lineage, myelin, and white matter in adult mice lacking the chemokine receptor CXCR2.

Oligodendrocyte precursor cell (OPC) proliferation and migration are critical for the development of myelin in the central nervous system (CNS). Previous studies showed that localized expression of the chemokine CXCL1 signals through the receptor CXCR2 to inhibit the migration and enhance the proliferation of spinal cord OPCs during development. Here, we report structural and functional alterations in the adult CNS of Cxcr2-/- mice.

Determinants of CCL5-driven mononuclear cell migration across the blood-brain barrier. Implications for therapeutically modulating neuroinflammation.

Chemokine receptors and adhesion molecules are used selectively for the transmigration of leukocytes across the blood-brain barrier (BBB) during neuroinflammation. We established an activated in vitro BBB (aIVBBB) using physiological concentrations of cytokines. We studied CCL5-driven migration as a model to determine how chemokine receptors and adhesion molecules regulate T-cell and monocyte migration across the aIVBBB.

Human cerebrospinal fluid contains CD4+ memory T cells expressing gut- or skin-specific trafficking determinants: relevance for immunotherapy.

Background: Circulating memory T cells can be divided into tissue-specific subsets, which traffic through distinct tissue compartments during physiologic immune surveillance, based on their expression of adhesion molecules and chemokine receptors. We reasoned that a bias (either enrichment or depletion) of CSF T cell expression of known organ-specific trafficking determinants might suggest that homing of T cells to the subarachnoid space could be governed by a CNS-specific adhesion molecule or chemokine receptor.

Results: The expression of cutaneous leukocyte antigen (CLA) and CC-chemokine receptor 4 (CCR4; associated with skin-homing) as well as the expression of integrin alpha4beta7 and CCR9 (associated with gut-homing) was analyzed on CD4+ memory T cells in CSF from individuals with non-inflammatory neurological diseases using flow cytometry.

Cutting edge: the silent chemokine receptor D6 is required for generating T cell responses that mediate experimental autoimmune encephalomyelitis.

D6, a promiscuous nonsignaling chemokine binding molecule expressed on the lymphatic endothelium, internalizes and degrades CC chemokines, and D6(-/-) mice demonstrated increased cutaneous inflammation following topical phorbol ester or CFA injection. We report that D6(-/-) mice were unexpectedly resistant to the induction of experimental autoimmune encephalomyelitis due to impaired encephalitogenic responses. Following induction with myelin oligodendroglial glycoprotein (MOG) peptide 35-55 in CFA, D6(-/-) mice showed reduced spinal cord inflammation and demyelination with lower incidence and severity of experimental autoimmune encephalomyelitis attacks as compared with D6(+/+) littermates.

Control of microglial neurotoxicity by the fractalkine receptor.

Microglia, the resident inflammatory cells of the CNS, are the only CNS cells that express the fractalkine receptor (CX3CR1). Using three different in vivo models, we show that CX3CR1 deficiency dysregulates microglial responses, resulting in neurotoxicity. Following peripheral lipopolysaccharide injections, Cx3cr1-/- mice showed cell-autonomous microglial neurotoxicity.

The neuronal chemokine CX3CL1/fractalkine selectively recruits NK cells that modify experimental autoimmune encephalomyelitis within the central nervous system.

Leukocyte trafficking to the central nervous system (CNS), regulated in part by chemokines, determines severity of the demyelinating diseases multiple sclerosis (MS) and experimental autoimmune encephalomyelitis (EAE). To examine chemokine receptor CX3CR1 in EAE, we studied CX3CR1(GFP/GFP) mice, in which CX3CR1 targeting by insertion of Green Fluorescent Protein (GFP) allowed tracking of CX3CR1+ cells in CX3CR1(+/GFP) animals and cells destined to express CX3CR1 in CX3CR1(GFP/GFP) knockouts. NK cells were markedly reduced in the inflamed CNS of CX3CR1-deficient mice with EAE, whereas recruitment of T cells, NKT cells and monocyte/macrophages to the CNS during EAE did not require CX3CR1.

Severe disease, unaltered leukocyte migration, and reduced IFN-gamma production in CXCR3-/- mice with experimental autoimmune encephalomyelitis.

Experimental autoimmune encephalomyelitis (EAE) is a CD4(+) Th1 T cell-mediated disease of the CNS, used to study certain aspects of multiple sclerosis. CXCR3, the receptor for CXCL10, CXCL9, and CXCL11, is preferentially expressed on activated Th1 T cells and has been proposed to govern the migration of lymphocytes into the inflamed CNS during multiple sclerosis and EAE. Unexpectedly, CXCL10-deficient mice were susceptible to EAE, leaving uncertain what the role of CXCR3 and its ligands might play in this disease model.

Alternative and accessory pathways in the regulation of IFN-beta-mediated gene expression.

Type I interferons (IFNs) induce the transcription of IFN-stimulated genes (ISGs) through activation of the Jak-Stat pathway. Although some determinants of specificity are dictated by the Jak-Stat components, recent observations indicate that the system incorporates other components for selectivity and flexibility, whose mechanisms remain to be defined. We identified a gene, beta-R1, which was induced relatively selectively by IFN-beta as compared with numerous IFN-alpha subtypes.

The expression and function of chemokines involved in CNS inflammation.

Chemokines and their receptors have principal roles in leukocyte trafficking under normal physiological and pathological conditions. The differential expression of the chemokine system in different parts of the CNS provides insights into the processes that are required for normal immune surveillance and pathological immune-mediated effector processes. Insights derived from studying multiple sclerosis, an inflammatory disorder of the CNS in humans, and experimental autoimmune encephalomyelitis, an animal model of this disorder, aid in further understanding the complexities of chemokine-mediated inflammation.

Chemokines in multiple sclerosis: CXCL12 and CXCL13 up-regulation is differentially linked to CNS immune cell recruitment.

Understanding the mechanisms of immune cell migration to multiple sclerosis lesions offers significant therapeutic potential. This study focused on the chemokines CXCL12 (SDF-1) and CXCL13 (BCA-1), both of which regulate B cell migration in lymphoid tissues. We report that immunohistologically CXCL12 was constitutively expressed in CNS parenchyma on blood vessel walls.