Virus-activated T cells regulate expression of adhesion molecules on endothelial cells in sites of infection

To study the role of cell adhesion molecules in the fatal CD8⁺ T-cell mediated meningitis which is induced by intracerebral infection with lymphocytic choriomenmgitis virus, the expression of relevant molecules on inflammatory cells and local endothelium was analyzed immunohistochemically. Most inflammatory cells were strongly positive for LFA-1, VLA-4, Pgp-1 and ICAM-1. Expression of ICAM-1 and VCAM-1 was upregulated on the endothelial cells in immunocompetent mice, but hot in T-cell deficient nude mice. analysis of mice deficient in either CD4⁺ or CD8⁺ T cells, revealed that not only was the inflammatory reaction dependent on the presence of CD8⁺ cells, but these cells also appeared to be required for maximal upregulation of ICAM-1 and VCAM-1 on the endothelial cells. These results indicate that virus-specific CD8⁺ T cells are crucially involved in regulating the inflammatory reaction through effects on endothelial expression of adhesion molecules.     

Activation and adhesion molecule expression on lymphoid infiltrates in human glioblastomas

Frozen tissue sections obtained from human glioblastomas, brain tumor metastases and normal brain were examined for the expression of molecules known to be involved in lymphocyte activation and/or adhesion and migration. The molecules studied included CD3, CD45R, UCHL-1 (CD45RO), lymphocyte function-associated antigen 1 (LFA-1) (CD11a, CD18), intercellular adhesion molecule 1 (ICAM-1) (CD54), 4B4 (CD29), CD44, CD2, and LFA-3 (CD58). CD3+ lymphocytes infiltrating human glioblastomas and brain tumor metastases expressed LFA-1 alpha and beta. Many cells were also UCHL-1+ whereas only a small percentage were CD45R+. CD2+ lymphocytes were also present. Tumor-infiltrating lymphocytes (TIL) were found to be negative for CD29, which was, however, expressed on intratumoral vessels in addition to vessels found in normal brain. Glioblastoma cells and intratumoral vessels expressed ICAM-1 whereas no ICAM-1 was found on TIL or on normal brain. Glioblastoma cells also expressed high levels of both CD44 and LFA-3 whereas TIL were negative for these antigens. CD44 was also expressed on certain regions of normal brain. Antibodies to LFA-1 alpha and -beta and ICAM-1 could significantly block the binding of lymphokine-activated killer (LAK) cells or TIL to human glioblastoma cells suggesting that these molecules play a role in the binding and subsequent migration of lymphocytes into brain tumor tissue.     

Effector and suppressor roles for LFA-1 during the development of experimental autoimmune encephalomyelitis

LFA-1 (CD11a/CD18) is a member of the β₂-integrin family of adhesion molecules important in leukocyte trafficking and activation. Although LFA-1 is thought to contribute to the development of experimental autoimmune encephalomyelitis (EAE) primarily through its functions on effector T cells, its importance on other leukocyte populations remains unexplored. To address this question, we performed both adoptive transfer EAE experiments involving CD11a^?/? mice and trafficking studies using bioluminescent T cells expressing luciferase under the control of a CD2 promoter (T-lux cells). Transfer of encephalitogenic CD11a^?/? T cells to wild type mice resulted in a significant reduction in overall EAE severity compared to control transfers. We also observed, using in vivo imaging techniques, that CD11a^?/? T-lux cells readily infiltrated lymph nodes and the CNS of wild type recipients with kinetics comparable to CD11a^+/+ transfers, although their overall numbers in these organs were reduced. Surprisingly, transfer of encephalitogenic wild type T cells to CD11a^?/? mice induced a severe and sometimes fatal EAE disease course, associated with massive T cell infiltration and proliferation in the CNS. These data indicate that LFA-1 expression on leukocytes in recipient mice plays an important immunomodulatory role in EAE. Thus, LFA-1 acts as a key regulatory adhesion molecule during the development of EAE, serving both pro- and anti-inflammatory roles in disease pathogenesis.     

Macrophage-independent T cell infiltration to the site of injury-induced brain inflammation

We have addressed the role of macrophages in glial response and T cell entry to the CNS after axonal injury, by using intravenous injection of clodronate-loaded mannosylated liposomes, in C57BL6 mice. As expected, clodronate-liposome treatment resulted in depletion of peripheral macrophages which was confirmed by F4/80- and MOMA-1(-) stainings in spleen. Sequential clodronate-liposome treatment 4, 2 and 0 days before axotomy resulted in significant reduction of infiltrating CD45(high) CD11b+ macrophages in the hippocampus at 1, 2 and 3 days post-lesion, measured by flow cytometry. There was a slight delay in the expansion of CD45(dim) CD11+ microglia in clodronate-liposome treated mice, but macrophage depletion had no effect on the percentage of infiltrating T cells in the lesion-reactive hippocampus. Lesion-induced TNFalpha mRNA expression was not affected by macrophage depletion, suggesting that activated glial cells are the primary source of this cytokine in the axonal injury-reactive brain. This identifies a potentially important distinction from inflammatory autoimmune infiltration in EAE, where macrophages are a prominent source of TNFalpha and their depletion prevents parenchymal T cell infiltration and disease.     

Expression of adhesion molecules and monocyte chemoattractant protein-1 (MCP-1) in the spinal cord lesions in HTLV-I-associated myelopathy

Leukocyte adhesion molecules to endothelium plays an important role in the pathogenesis of inflammatory diseases, including HTLV-I-associated myelopathy (HAM)/tropical spastic paraparesis (TSP). To help define the role of adhesion molecules in HAM/TSP, we studied the expression of lymphocyte function-associated antigen-1 (LFA-1), Mac-1, very late antigen-4 (VLA-4), Sialyl Lewis^x (SLex), intercelluar adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), endothelial leukocyte adhesion molecule-1 (ELAM-1) and monocyte chemoattractant protein-1 (MCP-1) in the spinal cord lesions of HAM/TSP. The results indicate that spinal cord lesions of HAM/TSP have greater VCAM-1 expression on endothelium compared with those of controls. Infiltrating mononuclear cells, especially perivascular lesions, expressed VLA-4. Although the expression of ICAM-1 in the spinal cords was not distinctive between HAM/TSP and controls, infiltrating mononulcear cells in the spinal cords of HAM/TSP strongly expressed LFA-1 and Mac-1. ELAM-1 was expressed on endothelium in the inactive-chronic lesions from three of five HAM/TSP, but was not detectable in the spinal cords of controls. SLex reaction was detectable on occasional perivascular cells in the spinal cord of HAM/TSP, but not in those of controls. MCP-1 was detectable on perivascular infiltrating cells and vascular endothelium in active-chronic lesions. This study suggests that VLA-4/VCAM-1 interaction may play an important role for lymphocyte migration into the central nervous system (CNS), and MCP-1 may also be involved in inflammatory cell recruitment to the CNS in HAM/TSP. Received: 4 September 1995 / Revised, accepted: 23 October 1995     

The immunopathology of adoptively transferred experimental allergic encephalomyelitis (EAE) in Lewis rats. Part 1. Immunohistochemical examination of developing lesions of EAE

In order to examine developing lesions of experimental allergic encephalomyelitis (EAE) at the preclinical stage, adoptive transfer of EAE was achieved in Lewis rats using spleen cells obtained from rats previously immunized with 50 micrograms of guinea pig myelin basic protein (MBP) in complete Freund's adjuvant. After cell transfer, all the recipient rats developed severe paraparesis with minimal variation in the onset of clinical signs, which facilitated immunohistochemical examination of developing lesions of EAE in asymptomatic animals. The initial pathological finding detected in this system was an increased number of inflammatory cells (both OX19+ and OX8+ T cells and macrophages) in the subarachnoid space (SAS) which was observed on day 3 post-transfer (PT) when the recipient animals showed no neurological abnormalities. By day 4 PT, inflammatory cells were detected in the Virchow-Robin space of vessels which were continuous to the SAS. Perivascular lymphocytic infiltration was scarcely detected in the gray matter. On day 5 PT, the rats showed severe paraparesis. Inflammatory foci increased in number and were detected in both the white and gray matter. Diffuse parenchymal T-lymphocyte infiltration was also recognized at this stage. From day 6 PT onwards, inflammatory cells decreased gradually. On day 8 PT, all the rats recovered from EAE and few inflammatory cells were detected in the parenchyma and SAS. Immunohistochemical examination of T-cell subsets and Ia antigens revealed that the number of OX19+ cells was greater than that of OX8+ cells in the parenchyma and SAS at all stages examined, the distribution of OX19+ cells was almost the same as that of OX8+ cells, OX8+ cells decreased in number before clinical signs subsided, and that after the infiltration of T cells into the parenchyma, cells with dendritic morphology (microglia) expressed Ia antigens in close association with the infiltrating T cells. Adoptive transfer of MBP-sensitized spleen cells provides constant induction of EAE with minimal variation in clinical onset and severity, thus being a useful model for the examination of early events of EAE.     

Inflammatory cells, microglia and MHC class II antigen-positive cells in the spinal cord of Lewis rats with acute and chronic relapsing experimental autoimmune encephalomyelitis

Chronic relapsing experimental autoimmune encephalomyelitis (CR-EAE) was induced in Lewis rats by inoculation with guinea pig spinal cord and adjuvants and treatment with low dose cyclosporin A (CsA). Acute EAE was induced by the same method without CsA treatment. Immunocytochemistry and flow cytometry were used to assess inflammatory cells and MHC class II (Ia) antigen expression in the central nervous system of these rats. The inflammatory infiltrate was composed mainly of CD4⁺ T cells and macrophages, and αß T cells constituted about 65% of the CD2⁺ T cells. After recovery from acute EAE and during the first remission of CR-EAE, the number of T cells was significantly less than in the preceding episodes. The number of T cells was higher in the second episode of CR-EAE than in the first remission. Throughout the course of CR-EAE, the majority of the CD2⁺ T cells were CD45RC⁻. The ratio of IL-2R⁺ cells to CD2⁺ cells ranged from 10.5 to 24.0%. The ratio of CD4⁺ T cells to B cells was lower in the later episodes of CR-EAE than in the first episode. Ia antigen was expressed on filtrating round cells at all stages of CR-EAE and on microglial cells (identified by dendritic morphology) with increasing intensity throughout the course of CR-EAE. With flow cytometry, the number of Ia⁺ cells obtained from the spinal cord rose throughout the course of CR-EAE. The number of FSC^lowOX1^low cells, which we consider represent microglia, also increased during the course of CR-EAE.     

Role of ICAM-1 in persisting inflammation in Parkinson disease and MPTP monkeys

It has been established that neuroinflammation is present in the substantia nigra (SN) of Parkinson disease (PD) cases but the factors responsible are as yet unknown. One contributing protein may be the intercellular adhesion molecule-1 (ICAM-1, CD54). ICAM-1 with its counter receptor, the lymphocyte function-associated antigen 1 (LFA-1) is known to play a key role in inflammatory processes and in T-cell mediated host defense mechanisms. We detected large numbers of ICAM-1-positive reactive astrocytes in the SN of a series of 14 patients with neuropathologically confirmed PD, including 3 of familial origin, compared with 11 age-matched controls. In PD SN, these ICAM-1-positive reactive astrocytes were particularly concentrated around many residual neurons in areas of heavy neuronal loss and extracellular melanin accumulation. LFA-1-positive reactive microglia gathered in areas of intense ICAM-1 expression, and LFA-1-positive leukocytes were identified infiltrating the tissue. Double immunostaining for ICAM-1 and LFA-1 revealed aggregates of reactive microglia embedded in areas of diffuse ICAM-1. Leukocyte counts were 5 fold higher in PD SN compared to controls (P < 0.001). Similar over-expression of ICAM-1 was found in monkeys that had been exposed to MPTP from 5.5 to 14 years previously compared with control monkeys. The presence of ICAM-1-positive reactive astrocytes in Parkinson disease and MPTP-treated monkeys is indicative of a sustained inflammatory process and suggests that antiinflammatory agents may have a place in PD therapy.     

CD1 expression is differentially regulated by microglia, macrophages and T cells in the central nervous system upon inflammation and demyelination

Expression of CD1 by microglia, macrophages and T cells was investigated ex vivo. In the healthy central nervous system (CNS), resident microglia, macrophages and T cells express levels of CD1 significantly lower than that expressed by splenic macrophages and T cells. During experimental autoimmune encephalomyelitis (EAE), CD1 expression by microglia and the number of CD1+ microglia increase. Macrophages and T cells strongly upregulate CD1 expression in the CNS, but not in the spleen. Whereas the function of CD1 expressed by T cells remains unclear, the expression by microglia and macrophages provides the CNS with a (glyco)lipidic-presenting molecule in an inflammatory and demyelinating environment.     

Substance P promotes lymphocyte-endothelial cell adhesion preferentially via LFA-1/ICAM-1 interactions

Substance P (SP), an 11 amino acid peptide, is released by C and A delta sensory nerve fibers during tissue insult and inflammation. We investigated the effect of SP on the expression and avidity of adhesion molecules, on lymphocytes and endothelial cells, which are central to the inflammatory cascade. Using in vitro adhesion assays we found that pretreatment of murine endothelial cells with SP enhanced their adhesiveness to splenocytes, the murine T cell hybridoma EL4 and nylon-enriched primary murine T cell in a dose and time dependent manner, the optimum dose being 10⁻¹⁰ M and the optimum time 6 h. SP at 10⁻¹⁰ M was also able to stimulate the splenocytes, EL4 T cells and primary T cells to enhance their adhesiveness for endothelial cells. The increased adhesiveness was associated with enhanced expression of ICAM-1 on endothelial cells and increased avidity of LFA-1 on lymphocytes. Further SP was chemotactic for T cells. These data suggest that SP modulates lymphocyte-endothelial cell interactions by preferentially upregulating LFA-1 and ICAM-1 interactions.     

Adhesion molecule expression on cerebrospinal fluid T lymphocytes: Evidence for common recruitment mechanisms in multiple sclerosis,aseptic meningitis,and normal controls

The expression of T-cell surface antigens was investigated in the cerebrospinal fluid (CSF) and peripheral blood of 11 patients with multiple sclerosis, 6 patients with aseptic meningitis, and 16 healthy subjects. A panel of monoclonal antibodies to adhesion and activation proteins was used in combination with an anti-CD3 antibody in dual-color flow cytometry. The problem of low cell numbers in the CSF from normal individuals was overcome by use of a modified staining procedure in microtiter plates, enabling analysis of as few as 5,000 cells. The majority of T cells in the CSF of the three patient groups exhibited the phenotype of memory cells (CD45RO⁺). CSF T cells also expressed significantly higher levels of several adhesion and activation molecules, including very late activation (VLA) antigens 3 through 6, lymphocyte function-associated (LFA) antigen 1, LFA-3, CD2, CD26, and CD44. Comparison between the different categories revealed that peripheral blood T cells from patients with multiple sclerosis expressed significantly lower amounts of the VLA integrins 4 and 5 as well as their common β subunit CD29, compared with normal control subjects. No differences between patients with multiple sclerosis and control subjects could, however, be seen regarding the distribution of memory/naive cells or CD4⁺/CD8⁺ cells in peripheral blood. Our data support a hypothesis that memory T cells with a high expression of several adhesion molecules are selectively recruited to the central nervous system compartment, under both pathological and normal conditions. We also provide evidence for an altered expression of adhesion molecules on peripheral blood T cells in patients with multiple sclerosis that is independent of the memory cell phenotype as defined by the expression of the CD45RO epitope.     

Regulation of leukocyte function-associated antigen 1-mediated adhesion by somatostatin and substance P in mouse spleen cells

BACKGROUND: Interaction of the integrin leukocyte function-associated antigen (LFA)-1 (CD11a/CD18) with its ligands, the intercellular adhesion molecules (ICAM)-1, -2, and -3 (CD54, CD102, and CD50), is pivotal to many leukocyte adhesion events. METHOD: To define the mechanism of the movement of leukocytes to the inflammatory site by somatostatin (SOM) and substance P (SP), we examined the expression of the adhesion molecule LFA-1 and inside-out signals for integrins, protein kinase C (PKC), Ras, Rap1, and phosphoinositide (PI) 3-kinase, in anti-CD3-, anti-CD3+SOM-, anti-CD3+SP-stimulated or unstimulated spleen cells. RESULTS: SOM caused down-regulation of LFA-1 mRNA translation as well as of adhesion-stimulating molecules such as Rap1, Ras, and PI 3-kinase. On the other hand, SP slightly induced LFA-1 mRNA translation and activation signals for integrins. The early-phase alteration of LFA-1 mRNA translation after 3 h of culture may be due to the changes of CD8+ T cells rather than changes of CD4+ cells. In adhesion assays, SOM significantly decreased cell adhesion (p < 0.05). CONCLUSION: These data suggest that SOM treatment of spleen cells, especially in CD8+ T cells, leads to downregulation of LFA-1 mRNA translation, inside-out signaling molecules for integrins (Ras, Rap1 and PI 3-kinase, but not PKC), and consequently to a decrease in the LFA-1-mediated adhesion to ICAM-1.     

Lymphokine induction of rat microglia multinucleated giant cell formation

Multinucleated giant cell formation (MNGC) occurs in central nervous system AIDS. The mechanism of fusion of microglia in these cases is unknown. We investigated the ability of lymphokines to induce fusion and found that interleukin-3 (IL-3), interleukin-4 (IL-4), gamma interferon (γ-IFN), and granulocyte-macrophage colony stimulating factor (GM-CSF) induced MNGC formation in cultures of rat microglia in vitro. The diacylglycerol analogue phorbol myristate acetate (PMA) also induced MNGC. Interleukin-1 (IL-1), interleukin-6 (IL-6), and tumor necrosis factor alpha (TNFα) failed to induce fusion. Preincubation of the IL-3 treated cultures with anti-IL-3, anti-leukocyte function associated antigen-1 (LFA-1) α-chain (CD11a), and anti-intercellular adhesion molecule-1 (ICAM-1) inhibited cell fusion. Antibody to polymorphic Class II major histocompatibility complex (MHC) determinants also inhibited MNGCs. Cell surface LFA-1 was predominantly observed on MNGC, suggesting that LFA-1 expression is involved in microglia fusion. We thus propose that MNGC formation of microglia result from the effects of T cell-derived cytokines probably through the induction of cell surface adhesion molecules. © 1993 Wiley-Liss, Inc.     

Expression of ICAM-1, VCAM-1, L-selectin, and leukosialin in the mouse central nervous system during the induction and remission stages of experimental allergic encephalomyelitis

Adhesion molecules facilitate infiltration of leukocytes into the central nervous system (CNS) of mice with experimental allergic encephalomyelitis (EAE). Expression of the adhesion molecules ICAM-1 (CD54), VCAM-1 (CD106), L-selectin (CD62L), and leukosialin (CD43) was analyzed via immunocytochemistry 4–28 days after the injection of encephalitogen into EAE-susceptible SWXJ mice. Constitutive ICAM-1 expression on large-diameter CNS vessels was upregulated on post-injection days 8, 11, 14 and 18 (concurrent with de novo expression on smaller capillaries and glial cells), partially downregulated by day 23, and back to control levels by day 28, Constitutive VCAM-1 expression was upregulated by day 14 and back to control levels by day 28. Upregulation of ICAM-1 temporally coincided with the immigration of CD4⁺ lymphocytes and L-selectin⁺ leukocytes into the CNS, while downregulation coincided with their emigration. The infiltration of CDA3⁺ leukocytes also coincided with the upregulation of vascular adhesion molecules, but CDA3⁺ cells remained in the CNS after ICAM-1 and VCAM-1 had returned to control levels. Cellular infiltration and adhesion-molecule expression preceded EAE clinical symptoms by a minimum of 3 days, suggesting a causal role of adhesion molecules in the initiation of CNS inflammation. However, prophylactic injections of monoclonal antibodies against either ICAM-1, L-selectin, or CD43, did not ameliorate the clinical severity of EAE in this model.     

Early influx of macrophages determines susceptibility to experimental allergic encephalomyelitis in Dark Agouti (DA) rats

Experimental allergic encephalomyelitis (EAE) is characterized by inflammatory infiltrates of myelin antigen(s) specific T cells and consecutive demyelination. Injection of encephalitogen into the footpads induces disease in genetically susceptible Dark Agouti rats (DA) but not in Albino Oxford (AO) rats although mild inflammatory infiltrates are observed in both strains early after disease induction. In addition, only DA rats develop disease when cells from (AO×DA) F(1) hybrids are passively transferred into sub-lethally radiated AO and DA parent hosts. The aim of the study was therefore to examine the participation of accessory cells, macrophages, dendritic cells and microglia in EAE development at the level of the target tissue in these two strains using specific membrane markers. We demonstrate here that in the induction phase of EAE in DA rats, macrophages (CD68(+); CD45(hi)CD11b(+)) are the first detectable infiltrating cells in the subpial regions of the spinal cord but were not found in AO rats. During the same period, resident microglial cells which are of the ramified variety are observed in both DA and AO rats. In DA rats at the peak of disease, when profuse influx of T cells is seen, macrophages and dendritic cells appear in the parenchyma of the CNS. In addition, at that time, microglial cells are activated. FACS analyses also reveal a significant increase in CD45(hi)CD11c(+) dendritic cells and CD45(hi)D11b(+) macrophages compared with levels in na?ve and immunized AO rats. During resolution of disease in DA rats, the expression of microglia and macrophage markers is comparable with those in na?ve non-immunized DA and immunized AO rats. We conclude that an initial influx of macrophages is indispensible for the development of EAE in DA rats. The presence of dendritic cells and myeloid dendritic cells at the peak of disease supports the role of these cells in EAE especially in relapses and chronicity. The activation pattern of microglia in DA rats does not indicate their role as antigen presenting cells in disease induction since they are ramified at the induction phase and only become activated after the overwhelming influx of T cells.     

Recent advances in the immunopathology of experimental autoimmune encephalomyelitis: With special reference to cytokine production in the central nervous system

Experimental autoimmune encephalomyelitis (EAE) is an inflammatory demyelinating disease that can be induced by immunization with encephalitogenic antigens such as myelin basic protein. Recent in vitro studies have demonstrated that cytokines play an important role in immune reactions in the central nervous system (CNS), suggesting that cytokines released by infiltrating cells and glial cells may contribute to the pathogenesis of EAE. In this review, we focus on the interactions between infiltrating cells and brain cells during the inflammatory process in EAE and discuss the roles of cytokines in the CNS. After immunization with proper myelin antigens, encephalitogenic T cells increase in number and infiltrate the CNS parenchyma via the subarachnoid space or the blood vessels. Once inflammatory cells infiltrate the CNS, microglia and astrocytes are activated, and some of these cells proliferate in response to cytokines released by infiltrating cells. Following this, activated microglia present antigens to induce T cell proliferation and cytokine production. In contrast, astrocytes induce T cell unresponsiveness, probably due to a lack of costimulatory signals. Furthermore, infiltrating T cells are the main producers of Th1 cytokines and are involved in T cell-brain cell interactions. This cascade of events indicates that immune reactions take place in the CNS, although the CNS has previously been considered to be an immunologically privileged site. Based on these findings, we also discuss the feasibility of using various cytokines to stimulate the immunomodulation of brain inflammation as a treatment for autoimmune demyelinating diseases.     

Th2 cells support intrinsic anti-inflammatory properties of the brain

In experimental autoimmune encephalomyelitis (EAE), Th1 cells are responsible for disease induction while Th2 cells can be protective. To address the mechanisms of this differential behavior, we utilized organotypic murine entorhinal-hippocampal slice cultures to analyze interactions between myelin basic protein-specific Th1 and Th2 cells with microglial cells. While both Th1 and Th2 cells induced CD40 expression, only Th1 cells induced intercellular adhesion molecule-1 (ICAM-1) expression on microglia. Moreover, Th2 cells prevented or even reversed Th1-induced ICAM-1 upregulation. Evidently, Th2 cells could diminish Th1-induced inflammatory reactions and actively support the resting state of microglia, which could be one mechanism of Th2-mediated remission of neuroinflammation during EAE.     

Adhesion molecule expression and regulation on cells of the central nervous system.

Cellular adhesion molecules were initially defined as cell surface structures mediating cell-cell and cell-extracellular matrix (ECM) interactions. Adhesion molecules involved in immune responses have been classified into three families according to their structure: selectins, immunoglobulin (Ig) superfamily, and integrins. It has been well documented that adhesion molecules of these family members (E-selectin, ICAM-1, and VCAM-1) are expressed on brain microvessel endothelial cells in active lesions of multiple sclerosis (MS) brain. In addition, accumulating data show that glial cells can express some of these adhesion molecules upon activation: astrocytes can express ICAM-1, VCAM-1, and E-selectin, and microglia express ICAM-1 and VCAM-1. In vitro studies show that these adhesion molecules are actively regulated by several cytokines which have relevance to MS or experimental autoimmune encephalomyelitis (EAE). In addition, soluble forms of adhesion molecules have been found in the serum and cerebrospinal fluid (CSF) of MS patients, and may be useful diagnostically. Experimental therapy of EAE using antibodies against several adhesion molecules clearly shows that adhesion molecules are critical for the pathogenesis of EAE. Thus far, the function of adhesion molecule expression on brain endothelial and glial cells has not been clearly elucidated. Studies on the possible role of adhesion molecules on brain endothelial and glial cells will be helpful in understanding their involvement in immune responses in the central nervous system (CNS).     

Cxcl10 enhances blood cells migration in the sub-ventricular zone of mice affected by experimental autoimmune encephalomyelitis

The peri-ventricular area of the forebrain constitutes a preferential site of inflammation in multiple sclerosis, and the sub-ventricular zone (SvZ) is functionally altered in its animal model experimental autoimmune encephalomyelitis (EAE). The reasons for this preferential localization are still poorly understood. We show here that, in EAE mice, blood-derived macrophages, T and B cells and microglia (Mg) from the surrounding parenchyma preferentially accumulate within the SvZ, deranging its cytoarchitecture. We found that the chemokine Cxcl10 is constitutively expressed by a subset of cells within the SvZ, constituting a primary chemo-attractant signal for activated T cells. During EAE, T cells and macrophages infiltrating the SvZ in turn secrete pro-inflammatory cytokines such as TNFα and IFNγ capable to induce Mg cells accumulation and SvZ derangement. Accordingly, lentiviral-mediated over-expression of IFNγ or TNFα in the healthy SvZ mimics Mg/microglia recruitment occurring during EAE, while Cxcl10 over-expression in the SvZ is able to increase the frequency of peri-ventricular inflammatory lesions only in EAE mice. Finally, we show, by RT-PCR and in situ hybridization, that Cxcl10 is expressed also in the healthy human SvZ, suggesting a possible molecular parallelism between multiple sclerosis and EAE.     

A role for alpha4-integrin in the pathology following Semliki Forest virus infection

Migration of cells into the central nervous system (CNS) is a pivotal step in the pathogenesis of immune-mediated diseases such as multiple sclerosis (MS), experimental allergic encephalomyelitis (EAE) and virus-induced demyelinating diseases. Such migration is dependent on expression of adhesion molecules. The expression of adhesion molecules in the CNS was studied in Biozzi ABH mice infected with Semliki Forest virus (SFV) A7(74) - an important demyelinating model of MS. Expression of LFA-1alpha/CD11a, LFA-1beta/CD18 and ICAM-1/CD56 were rapidly elevated and remained high whereas MAC-1, CD44 and VCAM-1/CD106 were less widely expressed. The alpha4-integrin VLA-4/CD49d was more specifically associated with CNS lesions. To identify the importance of VLA-4, CD44, ICAM-1 and MAC-1 in the pathogenesis of SFV infection, monoclonal antibodies that block these adhesion molecules were administered in vivo during infection. Anti-VLA-4 treatment dramatically reduced the cellular infiltrates and demyelination within the CNS but did not affect the clearance of virus while antibodies to CD44, ICAM and MAC-1 antibody treatment had no effect. This study demonstrates that SFV infection induces the expression of adhesion molecules within the CNS and that VLA-4 plays an important role in the development of inflammation and demyelination in the CNS following SFV infection.