T-Helper Cells & Cytokines In MS

Chemokines are secreted proteins that function as ChemoAttractants, mediating the recruitment of specific subsets of Leukocytes to sites of tissue damage and Immunological Reactions.

Chemokines may also function as AntiViral agents, since Viruses such as Human ImmunoDeficiency Virus Type 1 (HIV-1) use Chemokine Receptors as Co-Receptors for Viral entry.

This study examines whether Virus-induced Interferon, IFN-ß, or Immune-related Interferon, IFN-, affects the production of ß-Chemokines by CNS Microglia and Peripheral Monocytes.

When IFN-ß was used as the stimulus, induction of MIP-1, MIP-1ß, MCP-1, and RANTES mRNA and protein was observed within 12 h of stimulation in Microglia.

By contrast, when IFN- was used as the stimulus, only MCP-1 was induced.

IFN-ß stimulation of blood Monocytes resulted in upregulation of MIP-1, MIP-1ß, and MCP-1.

Thus, Type 1 and 2 Interferons differentially regulate ß-Chemokines in human fetal Microglia and Peripheral blood Monocytes.

These observations may have relevance for the therapeutic activity of IFN-ß in Multiple Sclerosis and for the AntiViral effects of IFN-ß for HIV-1 infection of Monocytes and Microglia.

Copyright 2000 Wiley-Liss, Inc.

Antigen-coupled Antigen Presenting Cells (APC) serve as potent ToleroGens for inhibiting Immune Responses in vivo and in vitro.

Apparently by providing an Antigen-specific signal through the TCR in the absence of co-stimulation. Although this approach has been well studied in rodents, little is known about its effects on human T-Cells.

We evaluated the specificity and mechanisms of Tolerization of human T-Cells in vitro using Monocyte-enriched adherent cells that were pulsed with Antigen and treated with, 1-Ethyl-3-(3-Dimethylaminopropyl)-Carbodiimide (ECDI).

Autologous Antigen-coupled APC selectively Tolerized T-Cells of the T-Helper 1 (Th1) but not Th2 lineage through a mechanism that involved both Antigen-Specific and Antigen-Non-Specific elements.

The Tolerization process was dependent on the ECDI and Antigen concentration, and the coupling time, and was reflected by initial up-regulation of CD25.

However, upon re-stimulation with fresh APC and Antigen, Tolerized Th1 Cells failed to proliferate or to produce Th1 Cytokine message or secreted protein.

They had decreased expression of CD25, CD28 and B7 and increased expression of MHC Class II molecules, and demonstrated an enhanced commitment to Apoptosis.

Th1 Cell Tolerization could be prevented by adding Anti-CD28 AntiBody, IL-2 or untreated APC at the same time as the ECDI/Antigen-coupled APC, or reversed by adding Anti-CD28 AntiBody or IL-2 upon re-stimulation with fresh APC plus Antigen.

Thus, the tolerizing effect of ECDI/Antigen-coupled APC on human Th1 Cells appears to involve a reversible Anergy mechanism leading to Apoptosis, whereby the targeted T-Cells receive full or partial activation through the TCR, without coordinate co-stimulation.

These data suggest DiChotomous signaling requirements for inactivating Cells of the Th1 and Th2 lineages that may have important implications for treatment of Th1-mediated AutoImmune or Inflammatory Diseases.

Objective
To determine whether the efficacy of Interferon-beta-1b (IFN-ß-1b) on lesion activity could be shown with annual analysis of MRI.

Background
Clinical outcomes and MRI burden of disease changes in MS patients in a multicenter double-blind placebo-controlled 5-year trial of IFN-ß-1b have been reported, together with an analysis of 6-weekly MRI activity in a small subgroup during 2 years.

MRI activity measurements based on annual scans have not been documented.

Methods
Patients were randomized into three treatment arms: placebo, 1.6 mIU, and 8 mIU IFN-ß-1b self-administered subcutaneously every other day. Active lesions were identified as new, enlarging, or recurrent on Proton Density and T₂-weighted MRI scans.

Gadolinium was not used. An annual accumulation activity index was developed as an additional analysis of lesion activity.

Results
During the 5 years, both high- and low-dose IFN-ß-1b groups showed a striking reduction in lesion annual accumulation activity on the activity index versus placebo (p = 0.001).

Thirty-five percent of the high-dose patients and 29% of the low-dose patients were MRI inactive by this method of analysis, whereas only 16% of placebo patients were inactive (p = 0.001, placebo versus 8 mIU).

Conclusions
This analysis of the annual accumulation of lesion activity shows that the previously reported treatment effect seen on MRI scanning once every 6 weeks in a subcohort of the patients can also be seen on yearly scans.

This annual accumulation activity analysis provides an independent MRI confirmation of a treatment and dose effect for IFN-ß-1b.

Suppression of CD4⁺ Th1 Cell-mediated AutoImmune Disease via Immune deviation is an attractive potential therapeutic approach.

CD4⁺ Th2 T-Cells specific for Myelin Basic Protein, induced by immunization of young adult male SJL mice, suppress or modify the progression of CNS AutoImmune Disease.

This report demonstrates that activation of Non-NeuroAntigen-specific Th2 Cells is sufficient to suppress both clinical and histological Experimental Allergic EncephaloMyelitis (EAE).

Th2 Cells were obtained following immunization of male SJL mice with keyhole Limpet Hemocyanin. Transfer of these cells did not modify EAE, a model of human Multiple Sclerosis, in the absence of cognate Ag.

Disease suppression was obtained following adoptive transfer and subcutaneous immunization.

Suppression was not due to the deletion of Myelin Basic Protein-specific T-Cells, but resulted from the presence of IL-10 as demonstrated by the inhibition of Th2-mediated EAE suppression via passive transfer with either anti-IL-10 or anti-IL-10R mAb.

These data demonstrate that peripheral activation of a CD4⁺ Th2 population specific for an Ag not expressed in the CNS modifies CNS AutoImmune Disease via IL-10.

These data suggest that either peripheral activation or direct administration of IL-10 may be of benefit in treating Th1-mediated AutoImmune Diseases.

Multiple Sclerosis (MS) is an Inflammatory, DeMyelinating disease that is specific to the Central Nervous System. Cytokines are thought to be key mediators of the AutoImmune attack against Central Nervous System Myelin in MS.

To investigate the involvement of Cytokines in MS, the mRNA levels of Interferon-gamma (IFN-), Tumor Necrosis Factor-alpha (TNF-), InterLeukin-4 (IL-4) and InterLeukin-10 (IL-10) in peripheral blood MonoNuclear Cells without stimulation in vitro were quantified by a competitive reverse transcription polymerase chain reaction technique.

The level of IL-10 specific mRNA was significantly decreased in 47 MS patients compared with 42 healthy controls (P<0.0001).

TNF- was significantly increased in MS patients compared with healthy controls (P=0.014), especially in the patients with Chronic/Progressive MS (P=0.0003). Thus we conclude that there are significant in vivo alterations in Cytokine Gene expression in the Periphery in MS.

During the past year significant advances have been made in our understanding of the factors contributing to the differentiation of CD4⁺ T-Helper Cell subsets.

These have been driven, in part, by the realization that Cytokines from the Innate Immune Response, such as InterLeukin-12 (IL-12) and Interferons (IFNs), play a critical role in T-Cell subset differentiation.

This review covers some of the most recent data concerning the divergent role that IFNs have in the differentiation of human versus mouse T-Helper Cell subsets.

In this review we discuss the molecular basis for the specie-specific effect of Type I IFN on the selective induction of Th1 type Immune Responses.

Furthermore, since IFN-ß is used in the treatment of Multiple Sclerosis (MS) we discuss the potential effects of such treatment and the value of the Th1/Th2 paradigm in MS.

Experimental Allergic EncephaloMyelitis (EAE) is a DeMyelinating Disease of the Central Nervous System which is an animal model for the human AutoImmune Disease, Multiple Sclerosis. EAE is mediated by CD4⁺ T-Cells and the T-Cells responsible for disease induction produce Th1 Cytokines.

IL-12 produced by Monocytes and Dendritic Cells is the most critical factor which influences the development and differentiation of Pathogenic AutoReactive Th1 cells.

Here, we review our recent studies on the critical contributions of IL-12 and the IL-12R ß 2 subunit to the generation of AutoReactive Effector Cells which mediate EAE.

In addition, we discuss the potential contribution of IL-18 to the upregulation of the IL-12/IL-12R ß 2 pathway and the contribution of the Suppressor Cytokines, IL-4 and IL-10, in downregulating this pathway.

Collectively, our studies demonstrate that the IL-12/IL-12R ß 2 pathway is a critical intermediary in the process of Th1 differentiation which can be both positively or negatively regulated.

This pathway remains an attractive ImmunoTherapeutic target for blockade of function with inhibitory reagents or downregulation by Th2 Cytokines.

Th1-polarized CD4⁺ T-Cells are considered central to the development of a number of target-directed AutoImmune Disorders including Multiple Sclerosis.

The APC-derived Cytokine IL-12 is a potent inducer of Th1 polarization in T-Cells. Inhibition of IL-12 in vivo blocks the development of Experimental Allergic EncephaloMyelitis (EAE), the animal model for Multiple Sclerosis.

Based on previous work that suggests that the production of IL-12 by activated human Central Nervous System-derived Microglia is regulated by Autocrine Tumor Necrosis Factor-alpha (TNF-).

We wanted to determine whether inhibition of TNF could induce a reduction of Th1 responses by its impact on systemic APCs (MHC II / Helper T-Cell Interactions).

We found that soluble TNFR p75-IgG fusion protein (TNFR:Fc) inhibited production of Interferon-gamma (IFN-) by allo-Ag-activated blood-derived human CD4⁺ T-Cells.

We documented reduced IL-12 p70 production by APCs in the MLR. By adding back recombinant IL-12, we could rescue IFN- production, indicating that TNFR:Fc acts on APC-derived IL-12.

Consistent with an inhibition of the Th1 polarization, we found a decreased expression of IL-12R-ß2 subunit on the T-Cells.

Furthermore, the capacity of T-Cells to secrete IFN- upon restimulation when previously treated with TNFR:Fc is impaired, whereas IL-2 secretion was not altered.