I-Tim-izing the pathways of counter-regulation

Dexamethasone reduces IL-17 and Tim-3 expression in BALF of asthmatic mice

This study investigated the expression of interleukin-17 (IL-17) and T cell immunoglobulin mucin and domain-containing molecule-3 (Tim-3) in bronchoalveolar lavage fluid (BALF) of asthmatic mice and the effect of dexamethasone (DEX) on these factors. Thirty-six mice were randomly divided into three groups: normal group, asthmatic group and DEX group. The mouse model of asthma was established by sensitization with ovalbumin in both the asthmatic and DEX groups. The levels of IL-6, IL-10, IL-17 and TGF-β were measured in BALF by enzyme-linked immunesorbent assay (ELISA). The mRNA expression level of Tim-3 was detected by reverse transcription polymerase chain reaction (RT-PCR). The ratio of Tim-3+CD4+ cells to total CD4+ cells in BALF was determined by flow cytometry. Differential inflammatory cells in BALF were detected. The correlations among IL-17, IL-6, IL-10, Tim-3 and inflammatory cells were analyzed. The results showed that the levels of IL-17, IL-6 and Tim-3 were substantially increased and the IL-10 level decreased in BALF in the asthmatic mice, which was significantly reversed by DEX treatment. IL-17 expression was positively correlated with IL-6 and Tim-3 expression and the number of inflammatory cells but negatively with IL-10 expression. These results indicate that the increased expression of IL-17 and Tim-3 in BALF may be implicated in the occurrence and development of asthmatic inflammation; the mechanism by which DEX suppresses asthmatic airway inflammation involves down-regulation of IL-17 and Tim-3 levels.

TIM-1 regulates macrophage cytokine production and B7 family member expression

T-cell immunoglobulin mucin-1 (TIM-1) is associated with the regulation of T helper type 2 (Th2) immune responses and has been associated with asthma susceptibility. Previous studies have shown that administration of TIM-1 results in T cell hyperproliferation and increased Th2 cytokine secretion. TIM-1 has also been shown to bind to macrophages, but the effects of TIM-1 administration on macrophage activity have not been assessed. In this study we demonstrate that TIM-1 binds to the mouse macrophage cell line RAW 264.7. Stimulation of the RAW264.7 cells with TIM-1 increases nitric oxide production. A dramatic increase in the pro-inflammatory cytokines TNF-alpha and IL-6 is seen upon TIM-1 stimulation of RAW 264.7 cells. Additionally, there is a moderate increase in the immuno-modulatory cytokine IL-10 when RAW 264.7 cells are stimulated with TIM-1. TIM-1 stimulation also alters the expression of some members of the B7 family of co-stimulatory/co-inhibitory proteins. TIM-1 stimulation leads to increased B7-1, B7-H1, and PD-L2 expression, while inhibiting B7-H2 expression. These studies suggest that TIM-1 can regulate macrophage activation and alter the co-stimulatory properties of macrophages and thus may contribute to allergic inflammatory diseases such as asthma.

Cutting Edge: T Cell Ig Mucin-3 Reduces Inflammatory Heart Disease by Increasing CTLA-4 during Innate Immunity

Autoimmune diseases can be reduced or even prevented if proinflammatory immune responses are appropriately down-regulated. Receptors (such as CTLA-4), cytokines (such as TGF-beta), and specialized cells (such as CD4+CD25+ T regulatory cells) work together to keep immune responses in check. T cell Ig mucin (Tim) family proteins are key regulators of inflammation, providing an inhibitory signal that dampens proinflammatory responses and thereby reducing autoimmune and allergic responses. We show in this study that reducing Tim-3 signaling during the innate immune response to viral infection in BALB/c mice reduces CD80 costimulatory molecule expression on mast cells and macrophages and reduces innate CTLA-4 levels in CD4+ T cells, resulting in decreased T regulatory cell populations and increased inflammatory heart disease. These results indicate that regulation of inflammation in the heart begins during innate immunity and that Tim-3 signaling on cells of the innate immune system critically influences regulation of the adaptive immune response.

Inhibition of in vitro and in vivo T cell responses by recombinant human Tim-1 extracellular domain proteins

Members of the T cell, Ig domain and mucin domain (Tim) family of proteins have recently been implicated in the control of T cell-mediated immune responses. Tim-1 (HUGO designation HAVCR1) polymorphisms have been linked to the regulation of atopy in mice and humans, suggestive of a role in immune regulation. Tim-1 is expressed upon activation of T cells. In concert with the increased expression of Tim-1, a binding partner for the extracellular domain of Tim-1 (eTim-1) was induced on activated T cells, and mRNA expression data was consistent with the binding partner being Tim-4. We found that co-immobilized recombinant eTim-1 was able to inhibit T cell activation mediated by CD3 + CD28 mAb. eTim-1 mediated its inhibitory effects on proliferation by arresting cell cycle at G(0)/G(1) phase through regulation of cell cycle proteins. In vivo, administration of eTim-1 proteins led to a decrease in both ear (contact hypersensitivity to oxazolone) and joint (methylated BSA antigen-induced arthritis) swelling. The inhibitory activity of eTim-1 in the T(h)1-dependent models was evidence that eTim-1 is able to modulate T cell responses. Manipulation of the Tim-1 interaction with its binding partner on T cells may therefore provide a novel target for therapeutic intervention in T cell-mediated diseases.