MicroRNA miR-155 Affects Antiviral Effector and Effector Memory CD8 T Cell Differentiation

MicroRNAs are key regulators of the immune response, but their role in CD8 T cell differentiation in vivo is not known. We show that miR-155 is important in both effector and memory antiviral CD8 T cell responses. Without miR-155, there was a weaker effector response and a skewing toward memory precursor cells. At the memory stage, miR-155-deficient CD8 T cells preferentially differentiated into central memory cells and were capable of mounting a potent secondary response

Bystander modulation of chemokine receptor expression on peripheral blood T lymphocytes mediated by glatiramer therapy

Background: Glatiramer acetate therapy is thought to be effective for multiple sclerosis (MS) by promoting TH2 cytokine deviation, possibly in the brain, but the exact mechanism and site of action are incompletely understood. Determining the site of action and effect of glatiramer on cell trafficking is of major importance in designing rational combination therapy clinical trials. Objective: To determine whether glatiramer therapy will also act in the peripheral blood through bystander modulation of chemokine receptor (CKR) expression and cytokine production on T lymphocytes. Design: Before-and-after trial. Setting: A university MS specialty center. Patients: Ten patients with relapsing-remitting MS. Interventions: Treatment with glatiramer for 12 months and serial phlebotomy. Main Outcome Measures: Cytokine production, CKR expression, and cell migration. Results: The glatiramer-reactive T cells were TH2 cytokine biased, consistent with previous studies. We found a significant reduction in the expression of the TH1 inflammation associated with the CKRs CXCR3, CXCR6, and CCR5 on glatiramer- and myelin-reactive T cells generated from patients with MS receiving glatiramer therapy vs baseline. Conversely, expression of the lymph node-homing CKR, CCR7, was markedly enhanced on the glatiramer-reactive T cells derived from patients with MS undergoing glatiramer therapy. There was a reduction in the percentage of CD4+ glatiramer-reactive T cells and an increase in the number of CD8+ glatiramer-reactive T cells. Conclusions: Glatiramer may suppress autoreactive CD4+ effector memory T cells and enhance CD8+ regulatory responses, and bystander modulation of CKRs may occur in the periphery. ©2005 American Medical Association. All rights reserved.Link_to_subscribed_fulltex

Activated T-cells inhibit neurogenesis by releasing granzyme B: Rescue by Kv1.3 blockers

There is a great need for pharmacological approaches to enhance neural progenitor cell (NPC) function particularly in neuroinflammatory diseases with failed neuroregeneration. In diseases such as multiple sclerosis and stroke, T-cell infiltration occurs in periventricular zones where NPCs are located and is associated with irreversible neuronal loss.We studied the effect of T-cellactivation on NPC functions. NPC proliferation and neuronal differentiation were impaired by granzyme B (GrB) released by the T-cells. GrB mediated its effects by the activation of a Gi-protein-coupled receptor leading to decreased intracellular levels of cAMP and subsequent expression of the voltagedependent potassium channel, Kv1.3. Importantly, blocking channel activity with margatoxin or blocking its expression reversed the inhibitory effects of GrB on NPCs. We have thus identified a novel pathway in neurogenesis. The increased expression of Kv1.3 in pathological conditions makes it a novel target for promoting neurorestoration. Copyright © 2010 the authors.Link_to_subscribed_fulltex

The voltage-gated Kv1.3 K(+) channel in effector memory T cells as new target for MS

Through a combination of fluorescence microscopy and patch-clamp analysis we have identified a striking alteration in K(+) channel expression in terminally differentiated human CCR7(–)CD45RA(–) effector memory T lymphocytes (T(EM)). Following activation, T(EM) cells expressed significantly higher levels of the voltage-gated K(+) channel Kv1.3 and lower levels of the calcium-activated K(+) channel IKCa1 than naive and central memory T cells (T(CM)). Upon repeated in vitro antigenic stimulation, naive cells differentiated into Kv1.3(high)IKCa1(low) T(EM) cells, and the potent Kv1.3-blocking sea anemone Stichodactyla helianthus peptide (ShK) suppressed proliferation of T(EM) cells without affecting naive or T(CM) lymphocytes. Thus, the Kv1.3(high)IKCa1(low) phenotype is a functional marker of activated T(EM) lymphocytes. Activated myelin-reactive T cells from patients with MS exhibited the Kv1.3(high)IKCa1(low) T(EM) phenotype, suggesting that they have undergone repeated stimulation during the course of disease; these cells may contribute to disease pathogenesis due to their ability to home to inflamed tissues and exhibit immediate effector function. The Kv1.3(high)IKCa1(low) phenotype was not seen in glutamic acid decarboxylase, insulin-peptide or ovalbumin-specific and mitogen-activated T cells from MS patients, or in myelin-specific T cells from healthy controls. Selective targeting of Kv1.3 in T(EM) cells may therefore hold therapeutic promise for MS and other T cell–mediated autoimmune diseases

Critical role for all-trans retinoic acid for optimal effector and effector memory CD8 T cell differentiation

A plethora of work implicates important effects of the Vitamin A derivative, retinoic acid (RA), in myeloid differentiation, while fewer studies explore the role of RA on lymphoid cells. Most work on lymphoid cells has focused on the influence of RA on CD4 T cells. There is little information about the role of RA in CD8 T cell differentiation, and even less on cell-intrinsic effects in the CD8 T cell. This study explores the role of RA on effector and memory differentiation in a cell intrinsic manner in the context of vaccinia virus infection. We observed the loss of the short-lived effector cell phenotype (reduced KLRG1+, T-bet(hi), granzyme B(hi)), accompanied by an enhanced memory precursor phenotype at the effector (increased CD127(hi), IL-2+) and contraction phase (increased CD127(hi), IL-2+, eomesodermin(hi)) of the CD8 response in the absence of RA signaling. The lack of RA also increased the proportion of central memory CD8s. Collectively; these results introduce RA in a new role in CD8 T cell activation and differentiation. This may have significant implication in optimal vaccine design where Vitamin A supplementation is used to augment effector responses, but this may be to the detriment of the long-term central memory response