Mikhail Pashenkov

Recruitment of dendritic cells to the cerebrospinal fluid in bacterial neuroinfections

Dendritic cells (DC) accumulate in the CNS during inflammation and may contribute to local immune responses. Two DC subsets present in human cerebrospinal fluid (CSF) are probably recruited from myeloid (CD11c(+)CD123(dim)) and plasmacytoid (CD11c(-)CD123(high)) blood DC. In bacterial meningitis and especially in Lyme meningoencephalitis, numbers of myeloid and plasmacytoid DC in CSF were increased, compared to non-inflammatory neurological diseases, and correlated with chemotactic activity of CSF for immature monocyte-derived DC (moDC). Multiple DC chemoattractants, including macrophage inflammatory protein (MIP)-1beta, monocyte chemotactic protein (MCP)-1, MCP-3, RANTES and stromal cell-derived factor (SDF)-1alpha were elevated in CSF in these two neuroinfections. Chemotaxis of immature moDC induced by these CSFs could be partially inhibited by mAbs against CXCR4, the receptor for SDF-1alpha, and CD88, the receptor for C5a. SDF-1alpha present in CSF also chemoattracted mature moDC, which in vivo could correspond to a diminished migration of antigen-bearing DC from the CSF to secondary lymphoid organs. Regulation of DC trafficking to and from the CSF may represent a mechanism of controlling the CNS inflammation.

Multiple sclerosis: pro- and anti-inflammatory cytokines and metalloproteinases are affected differentially by treatment with IFN-beta.

Interferon-beta (IFN-beta) has a beneficial influence on the course of multiple sclerosis (MS) and has become standard treatment of this disease, though its mechanisms of action are incompletely understood. This study examines the effect of IFN-beta treatment on the cytokines IL-6, TNF-alpha, IFN-gamma and IL-10; the metalloproteinases MMP-3, -7 and -9 and the tissue inhibitor of metalloproteinase-1 (TIMP-1). IFN-beta treatment resulted in decreased numbers of mononuclear cells (MNC) secreting IL-6 and TNF-alpha and expressing mRNA of MMP-3 and MMP-9 compared to pretreatment levels. On the contrary, numbers of IL-10 secreting MNC and TIMP-1 mRNA expressing were augmented during IFN-beta therapy. Whether the down-regulatory effects on pro-inflammatory and upregulatory effects on anti-inflammatory molecules are a direct result of IFN-beta on the immune system or secondary to clinical stabilization of MS pathology induced by IFN-beta remains to be evaluated.

Secondary lymphoid organ chemokines are elevated in the cerebrospinal fluid during central nervous system inflammation

Secondary lymphoid organ chemokines have been implicated in chronic inflammation. Their expression in the central nervous system (CNS) has not been studied. Here, levels of secondary lymphoid organ chemokines CCL19 (Exodus-3, MIP-3beta), CCL21 (Exodus-2, 6Ckine, SLC) and CXCL12 (SDF-1alpha) were analysed by ELISA in cerebrospinal fluid (CSF) and plasma from patients with multiple sclerosis (MS); acute optic neuritis (ON) with oligoclonal IgG in the CSF (i.e., first bout of MS); acute ON without oligoclonal IgG (non-MS-type ON); other inflammatory neurological diseases (OIND); and non-inflammatory neurological diseases (NIND). NIND CSF contained CCL19 and CXCL12, while CCL21 was not detected. Intrathecal production of CCL19 and CCL21 was elevated in MS, MS-type ON, and OIND, but not in non-MS-type ON. In MS, CSF levels of CCL19 weakly correlated with CSF cell counts. Intrathecal production of CXCL12 was elevated only in OIND. The role of elevated CCL19 and CCL21 in MS could be retention of mature dendritic cells (DC) in the CNS, recruitment of nai;ve T cells and activated B cells, as well as de novo formation of secondary lymphoid structures in MS plaques.

Inflammation in the Central Nervous System: the Role for Dendritic Cells

Dendritic cells (DCs) are a subclass of antigen‐presenting cells critical in the initiation and regulation of adaptive immunity against pathogens and tumors, as well as in the triggering of autoimmunity. Recent studies have provided important knowledge regarding distribution of DCs in the central nervous system (CNS) and their role in intrathecal immune responses. DCs are present in normal meninges, choroid plexus, and cerebrospinal fluid, but absent from the normal brain parenchyma. Inflammation is accompanied by recruitment and/or development of DCs in the affected brain tissue. DCs present in different compartments of the CNS are likely to play a role in the defence against CNS infections, and also may contribute to relapses/chronicity of CNS inflammation and to break‐down of tolerance to CNS autoantigens. CNS DCs can therefore be viewed as a future therapeutic target in chronic inflammatory diseases such as multiple sclerosis.

Multiple sclerosis and optic neuritis: CCR5 and CXCR3 expressing T cells are augmented in blood and cerebrospinal fluid

Abstract. A role for chemokines as mediators of Th1 cell recruitment to the central nervous system (CNS) is probable in MS. Therefore we studied expression of Th1-related CCR5 and CXCR3 chemokine receptors in patients with MS and controls. Patients with untreated MS had elevated percentages of CCR5 and CXCR3 expressing T cells vs. healthy controls (HC) in blood, and vs. other non-inflammatory neurological diseases (OND) patients in CSF. Such elevation was not found in MS patients examined during ongoing treatment with IFN-β. Patients with optic neuritis (ON), a common first manifestation of MS, had elevated percentages of CXCR3 expressing T cells in blood compared with HC, and of CCR5 expressing T cells in CSF compared with OND patients. High chemokine receptor expression may be one prerequisite for Th1 cells to migrate to the CNS. Inhibition of chemokine receptor expression may constitute a potentially important therapeutic effect of IFN-β.

Monocyte-derived dendritic cells express and secrete matrix-degrading metalloproteinases and their inhibitors and are imbalanced in multiple sclerosis

Dendritic cells (DC) are antigen-presenting cells (APC) that most efficiently initiate and control immune responses. Migration processes of blood DC are crucial to exert their professional antigen-presenting functions. Matrix-degrading metalloproteinases (MMP) are proteolytic enzymes, which are considered to be key enzymes in extracellular matrix (ECM) turnover and mediators of cell migration. Tissue inhibitors of metalloproteinases (TIMP) are important regulators of MMP activity. Here we investigate whether blood monocyte-derived immature DC (iDC) and mature DC (mDC) express, produce and secrete functionally active MMP-1, -2, -3 and -9 and their inhibitors TIMP-1 and -2, and examine their involvement in multiple sclerosis (MS). On mRNA level, we observed high numbers of MMP-2 and TIMP-2 mRNA expressing iDC in MS. On protein level, high percentages of MMP-1, -2 and -9 expressing iDC by flow cytometry, and high MMP-1 secretion by Western blot together with high MMP-2 and -9 activities in iDC supernatants as studied with zymography were observed. Similarly, MS is associated with high percentages of MMP-2 and -3 and of TIMP-1 expressing mDC by flow cytometry together with high MMP-3 secretion and high MMP-9 activity in culture supernatants. Spontaneous migratory capacity of both iDC and mDC over ECM-coated filters was higher in MS compared to healthy controls (HC). In conclusion, blood monocyte-derived iDC and mDC express, produce and secrete several MMP and TIMP. Alterations in these molecules as observed in MS may be functionally important for DC functioning.

Aberrated Levels of Cerebrospinal Fluid Chemokines in Guillain-Barré Syndrome and Chronic Inflammatory Demyelinating Polyradiculoneuropathy

Infiltration of spinal nerve roots and peripheral nerves by macrophages and T cells are rather consistent immunopathologic findings in patients with Guillain-Barré syndrome (GBS) and chronic inflammatory demyelinating polyradiculoneuropathy (CIDP). Chemokines play a central role in recruitment of leukocytes to inflamed tissue. Chemokines have been implicated in the pathogenesis of the experimental autoimmune neuritis (EAN), which represents an animal model of GBS, but the role of chemokines in GBS and CIDP is not clear. Since chemokines may be released into CSF from inflamed spinal nerve roots, we studied the concentrations of the chemokines MCP-1, MIP-1β, MIP-3β, IP-10, SDF-1α, RANTES, and SLC in the CSF by sandwich ELISA in patients over the course of GBS and CIDP, before and after immunomodulatory treatment. Controls consisted of patients with noninflammatory neurological disorders. Patients examined in the acute phase of GBS prior to treatment with intravenous high dose immunoglobulins (IvIg) had elevated CSF levels of MCP-1 (a chemoattractant for blood monocytes and dendritic cells) and IP-10 (a chemoattractant for T cells). Patients with CIDP examined prior to immunomodulatory treatment had elevated CSF levels of MIP-3β (a chemoattractant for mature dendritic cells, naïve and recently activated T cells) and IP-10. Levels of MIP-3β tended to decreased during follow-up in those CIDP patients responding favorably to immunomodulatory treatment. CSF levels of MCP-1 and IP-10 correlated with the CSF:plasma albumin ratio in both GBS and CIDP patients. In CIDP patients, CSF levels of MIP-3β also correlated with the CSF7colon;plasma albumin ratio. These data implicate MCP-1 and IP-10 in the pathogenesis of GBS, and IP-10 and MIP-3β in the pathogenesis of CIDP.

Elevated expression of CCR5 by myeloid (CD11c+) blood dendritic cells in multiple sclerosis and acute optic neuritis

Myeloid and plasmacytoid dendritic cells (DC) are present in cerebrospinal fluid (CSF) in non‐inflammatory neurological diseases (NIND) and elevated in clinically definite multiple sclerosis (MS) and in early MS – acute monosymptomatic optic neuritis (ON). Here, we show that expression of CCR5, a chemokine receptor for regulated on activation, normal T cell expressed and secreted (RANTES) and macrophage inflammatory protein (MIP)‐1α/β, is elevated on blood myeloid (CD11c+) DC in MS and ON compared to non‐inflammatory controls. In contrast, expression of CXCR4, a receptor for stromal cell‐derived factor (SDF)‐1α, is similar in all groups. Blood myeloid DC from MS patients respond chemotactically to RANTES and MIP‐1β, which are expessed in MS lesions. In active MS and ON, expression of CCR5 by myeloid DC in blood correlates with numbers of these cells in CSF. Thus, elevation of CCR5 may contribute to recruitment of myeloid DC to CSF in MS and ON. Recruitment of plasmacytoid DC to CSF appears to be CCR5‐independent.

Chemokines are produced in the brain early during the course of experimental African trypanosomiasis.

African trypanosomiasis is characterized by progressive central nervous system (CNS) involvement. Using single and double immunohistochemistry, we evaluated the induction of alpha- and beta-chemokines in brains of Sprague-Dawley rats infected with Trypanosoma brucei brucei (T. b. brucei) and identified their cellular source. The results showed high production of MIP-2, RANTES and MIP-1alpha and to a lower extend MCP-1 in infected animals compared to controls. MIP-2, RANTES and MIP-1alpha were produced early by astrocytes and microglia and later by macrophages and T-cells. These findings suggest that chemokines may contribute to the immunopathogenesis that occurs in the CNS early during infections.

Multiple sclerosis: a study of chemokine receptors and regulatory T cells in relation to MRI variables

Magnetic resonance imaging (MRI) remains the most valuable tool for monitoring disease activity and progression in patients with multiple sclerosis (MS), a chronic demyelinating disease of the central nervous system (CNS) with presumably autoimmune etiology. Chemokine receptors have been implicated in MS as key molecules directing inflammatory cells into the CNS. Regulatory (CD4+CD25+) T cells (Tr cells) are important in suppressing autoimmunity, and their absolute or functional deficit could be expected in MS. In the present study, venous blood was obtained from MS patients concurrent with MRI examination of the brain, and expression of chemokine receptors CCR1, CCR2, CCR5, CXCR3 and CXCR4 by CD4 T cells and monocytes, proportions of Tr cells, as well as expression of CD45RO, CD95, CTLA‐4, HLA‐DR and interleukin (IL)‐10 by Tr cells and non‐Tr (CD25−) CD4 T cells was analyzed by flow cytometry. Surface expression of CXCR3 by CD4 T cells was downregulated in the group of patients with high lesion load (LL) on T2‐weighted images and gadolinium (Gd)‐enhancing lesions on T1‐weighted images, compared to the group with high LL and no Gd‐enhancing lesions, and to the group with low LL, suggesting internalization of CXCR3 due to the release of its chemokine ligand (IP‐10/CXCL10) from active MS lesions. Proportions of Tr cells amongst all CD4 T cells, and expression of IL‐10 by Tr cells were increased in the patients with high LL and Gd‐enhancing lesions. These results suggest that there is correlation between MRI parameters, chemokine receptor expression and the status of circulating Tr cells in MS, but further studies need to discriminate between pathogenetically relevant and bystander phenomena.