[Show abstract][Hide abstract] ABSTRACT: T cells slow their motility, increase adherence, and arrest after encounters with antigen-presenting cells (APCs) bearing peptide-MHC complexes. Here, we analyzed the cell-cell communication among activating T cells. In vivo and in vitro, activating T cells associated in large clusters that collectively persisted for >30 min, but they also engaged in more transient interactions, apparently distal to APCs. Homotypic aggregation was driven by LFA-1 integrin interactions. Ultrastructural analysis revealed that cell-cell contacts between activating T cells were organized as multifocal synapses, and T cells oriented both the microtubule-organizing complex and interleukin-2 (IL-2) secretion toward this synapse. T cells engaged in homotypic interactions more effectively captured IL-2 relative to free cells. T cells receiving paracrine synaptic IL-2 polarized their IL-2 signaling subunits into the synaptic region and more efficiently phosphorylated the transcription factor STAT5, likely through a synapse-associated signaling complex. Thus, synapse-mediated cytokine delivery accelerates responses in activating T cells.
[Show abstract][Hide abstract] ABSTRACT: Surface molecules that are differentially expressed on Th1 and Th2 cells may be useful in regulating specific immune responses in vivo. Using a panel of mAbs, we have identified murine CD226 as specifically expressed on the surface of differentiated Th1 cells but not Th2 or Th0 cells. Although CD226 is constitutively expressed on CD8 cells, it is up-regulated on CD4 cells upon activation. Th1 differentiation results in enhanced CD226 expression, whereas expression is down-regulated upon Th2 polarization. We demonstrate that CD226 is involved in the regulation of T cell activation; in vivo treatment with anti-CD226 results in significant reduction of Th1 cell expansion and in the induction of APCs that inhibit T cell activation. Furthermore, anti-CD226 treatment delays the onset and reduces the severity of a Th1-mediated autoimmune disease, experimental autoimmune encephalomyelitis. Our data suggest that CD226 is a costimulatory molecule that plays an important role in activation and effector functions of Th1 cells.
Full-text · Article · Sep 2005 · The Journal of Immunology
[Show abstract][Hide abstract] ABSTRACT: Identification of the T cell immunoglobulin mucin-domain containing (Tim) gene family introduced a new family of cell surface molecules that is involved in the regulation of immune responses. We previously demonstrated that Tim-3 is expressed on terminally differentiated T helper (Th)1 cells, and serves to regulate Th1 immune responses. Here, we describe the identification and function of Tim-2, a novel member of the Tim gene family. In contrast with Tim-3, we demonstrate that Tim-2 is expressed preferentially in differentiated Th2 cells. Blockade of the Tim-2/Tim-2 ligand interaction, by administration of soluble Tim-2 fusion protein (Tim-2 immunoglobulin [Ig]), results in T cell hyperproliferation and the production of Th2 cytokines. Administration of Tim-2 Ig during the induction phase reduces the severity of experimental autoimmune encephalomyelitis, a Th1-mediated autoimmune disease model of multiple sclerosis. We propose that Tim-2, an orthologue of human Tim-1, is critical for the regulation of Th2 responses during autoimmune inflammation.
Full-text · Article · Sep 2005 · Journal of Experimental Medicine
[Show abstract][Hide abstract] ABSTRACT: The recently identified TIM gene family encodes cell-surface receptors that are involved in the regulation of Th1- and Th2-cell-mediated immunity. Tim-3 protein is specifically expressed on Th1 cells and negatively regulates Th1 responses, whereas Tim-2 is preferentially expressed in Th2 cells. Tim-1, previously identified as the hepatitis A virus receptor, co-stimulates T-cell expansion and cytokine production. Tim-4, which is preferentially expressed on mature dendritic cells, is the ligand for Tim-1. In mouse models of asthma and multiple sclerosis, affecting the function of Tim molecules altered disease phenotype. Because TIM molecules are differentially expressed on effector Th1 and Th2 cells, further understanding of the mechanisms by which they regulate Th1- and Th2-effector functions will probably provide opportunities for the therapeutic modulation of immune-mediated diseases.
No preview · Article · Sep 2005 · Trends in Molecular Medicine
[Show abstract][Hide abstract] ABSTRACT: Although T helper (T(H)) cell-mediated immunity is required to effectively eliminate pathogens, unrestrained T(H) activity also contributes to tissue injury in many inflammatory and autoimmune diseases. We report here that the T(H) type 1 (T(H)1)-specific Tim-3 (T cell immunoglobulin domain, mucin domain) protein functions to inhibit aggressive T(H)1-mediated auto- and alloimmune responses. Tim-3 pathway blockade accelerated diabetes in nonobese diabetic mice and prevented acquisition of transplantation tolerance induced by costimulation blockade. These effects were mediated, at least in part, by dampening of the antigen-specific immunosuppressive function of CD4(+)CD25(+) regulatory T cell populations. Our data indicate that the Tim-3 pathway provides an important mechanism to down-regulate T(H)1-dependent immune responses and to facilitate the development of immunological tolerance.
Full-text · Article · Dec 2003 · Nature Immunology
[Show abstract][Hide abstract] ABSTRACT: T helper type 1 (T(H)1) immune responses are central in cell-mediated immunity, and a T(H)1-specific cell surface molecule called Tim-3 (T cell immunoglobulin domain, mucin domain) has been identified. Here we report the identification of a secreted form of Tim-3 that contains only the immunoglobulin (Ig) variable (V) domain of the full-length molecule. Fusion proteins (Tim-3-Ig) of both Tim-3 isoforms specifically bound CD4(+) T cells, indicating that a Tim-3 ligand is expressed on CD4(+) T cells. Administration of Tim-3-Ig to immunized mice caused hyperproliferation of T(H)1 cells and T(H)1 cytokine release. Tim-3-Ig also abrogated tolerance induction in T(H)1 cells, and Tim-3-deficient mice were refractory to the induction of high-dose tolerance. These data indicate that interaction of Tim-3 with Tim-3 ligand may serve to inhibit effector T(H)1 cells during a normal immune response and may be crucial for the induction of peripheral tolerance.
Full-text · Article · Dec 2003 · Nature Immunology