Immunopathology of CD4+ T Cell-Mediated Autoimmune Responses to Central Nervous System Antigens: Role of IL-16

Multiple sclerosis (MS) is a chronic, inflammatory, demyelinating and degenerative disease of the central nervous system (CNS). While etiology of the disease remains unknown, genetic susceptibility and autoimmune mechanisms in the initiation and progression of the disease have been strongly suggested. Experimental autoimmune encephalomyelitis (EAE) is commonly used to study immune regulation of MS. Infiltration by CD4+ T cells, through blood-brain barrier (BBB), precedes the onset and relapses of MS. CNS migration and homing patterns of T cells are tightly synchronized by astrocyte and microglia derived cytokines and chemokines. Autoimmune, CNS antigenreactive, infiltrating T cells produce and locally release cytokines including but not limited to IFNγ, IL-2, IL-6, IL-16, IL-17, TNFα, and chemokines including CCL2, CCL5 and CXCL10. Chemokine mediated chemotaxis is exclusive for activated cell state and most chemokines do not discriminate between distinct cell types. Conversely, a cytokine IL-16 is a CD4-specific cytokine-ligand and exclusively induces chemotaxis of CD4+T cells, by binding and signaling through CD4, regardless of T cell activation state. In this article we focus on CD4+ T cell-mediated autoimmune responses to CNS antigens because of their importance for immunopathology of MS and EAE. We focus on autoimmune responses to myelin oligodendrocyte glycoprotein (MOG) because of its relevance for immunopathology of MS. We emphasize a role of IL-16 in regulation of CD4+T cell mediated autoimmune responses to MOG in EAE and MS. While a role of IL-16 in regulation of other CD4+T cell mediated autoimmune diseases has been established, its role in regulation of MS remains to be determined. Emerging data from our laboratories have indicated that IL-16-mediated CD4+ T cell chemoattraction has a significant role in regulation of CD4+ T cell-mediated autoimmune responses to CNS antigens. We propose an important function of this cytokine in regulation of relapsing-remitting EAE

Local Delivery of Interleukin 4 by Retrovirus-Transduced T Lymphocytes Ameliorates Experimental Autoimmune Encephalomyelitis

Experimental autoimmune encephalomyelitis (EAE) is an inflammatory autoimmune disease of the central nervous system which serves as a model for the human disease multiple sclerosis. We demonstrate here that encephalitogenic T cells, transduced with a retroviral gene, construct to express interleukin 4, and can delay the onset and reduce the severity of EAE when adoptively transferred to myelin basic protein–immunized mice. Thus, T lymphocytes transduced with retroviral vectors can deliver “regulatory cytokines” in a site-specific manner and may represent a viable therapeutic strategy for the treatment of autoimmune disease

Prolonged mitotic arrest induces a caspase-dependent DNA damage response at telomeres that determines cell survival

A delay in the completion of metaphase induces a stress response that inhibits further cell proliferation or induces apoptosis. This response is thought to protect against genomic instability and is important for the effects of anti-mitotic cancer drugs. Here, we show that mitotic arrest induces a caspase-dependent DNA damage response (DDR) at telomeres in non-apoptotic cells. This pathway is under the control of Mcl-1 and other Bcl-2 family proteins and requires caspase-9, caspase-3/7 and the endonuclease CAD/DFF40. The gradual caspase-dependent loss of the shelterin complex protein TRF2 from telomeres promotes a DDR that involves DNA-dependent protein kinase (DNA-PK). Suppression of mitotic telomere damage by enhanced expression of TRF2, or the inhibition of either caspase-3/7 or DNA-PK during mitotic arrest, promotes subsequent cell survival. Thus, we demonstrate that mitotic stress is characterised by the sub-apoptotic activation of a classical caspase pathway, which promotes telomere deprotection, activates DNA damage signalling, and determines cell fate in response to a prolonged delay in mitosis

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Atheroprotective Vaccination with MHC-II Restricted Peptides from ApoB-100

Background: Subsets of CD4+ T-cells have been proposed to serve differential roles in the development of atherosclerosis. Some T-cell types are atherogenic (T-helper type 1), while others are thought to be protective (regulatory T-cells). Lineage commitment toward one type of helper T-cell versus another is strongly influenced by the inflammatory context in which antigens are recognized. Immunization of atherosclerosis-prone mice with low density lipoprotein (LDL) or its oxidized derivative (ox-LDL) is known to be atheroprotective. However, the antigen specificity of the T-cells induced by vaccination and the mechanism of protection are not known.Methods: Identification of two peptide fragments (ApoB3501-3516 and ApoB978-993) from murine ApoB-100 was facilitated using I-Ab prediction models, and their binding to I-Ab determined. Utilizing a vaccination scheme based on complete and incomplete Freund’s adjuvant (1x CFA + 4x IFA), we immunized Apoe-/- mice with ApoB3501-3516 or ApoB978-993 emulsified in CFA once and subsequently boosted in IFA four times over 15 weeks. Spleens, lymph nodes and aortas were harvested and evaluated by flow cytometry and real time RT-PCR. Total atherosclerotic plaque burden was determined by aortic pinning and by aortic root histology.Results: Mice immunized with ApoB3501-3516 or ApoB978-993 demonstrated 40% reduction in overall plaque burden when compared to adjuvant only control mice. Aortic root frozen sections from ApoB3501-3516 immunized mice showed a >60% reduction in aortic sinus plaque development. Aortas from both ApoB3501-3516 and ApoB978-993 immunized mice contained significantly more mRNA for IL-10. Both antigen-specific IgG1 and IgG2c titers were elevated in ApoB3501-3516 or ApoB978-993 immunized mice, suggesting helper T-cell immune activity after immunization.Conclusion: Our data show that MHC Class II restricted ApoB-100 peptides can be atheroprotective, potentially through a mechanism involving elevated IL-10