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Specific inhibition of T‐cell adhesion to extracellular matrix and proinflammatory cytokine secretion by human recombinant galectin‐1

The migration of immune cells through the extracellular matrix (ECM) towards inflammatory sites is co‐ordinated by receptors recognizing ECM glycoproteins, chemokines and proinflammatory cytokines. In this context, galectins are secreted to the extracellular milieu, where they recognize poly‐N‐acetyllactosamine chains on major ECM glycoproteins, such as fibronectin and laminin. We investigated the possibility that galectin‐1 could modulate the adhesion of human T cells to ECM and ECM components. T cells were purified from human blood, activated with interleukin‐2 (IL‐2), labelled, and incubated further with intact immobilized ECM and ECM glycoproteins in the presence of increasing concentrations of human recombinant galectin‐1, or its more stable, related, C2‐S molecule obtained by site‐directed mutagenesis. The presence of galectin‐1 was shown to inhibit T‐cell adhesion to intact ECM, laminin and fibronectin, and to a lesser extent to collagen type IV, in a dose‐dependent manner. This effect was specifically blocked by anti‐galectin‐1 antibody and was dependent on the lectin’s carbohydrate‐binding properties. The inhibition of T‐cell adhesion by galectin‐1 correlates with the ability of this molecule to block the re‐organization of the activated cell’s actin cytoskeleton. Furthermore, tumour necrosis factor‐α (TNF‐α) and interferon‐γ (IFN‐γ) production was markedly reduced when IL‐2‐activated T cells were incubated with galectin‐1 or its mutant. This effect was prevented by β‐galactoside‐related sugars. The present study reveals an alternative inhibitory mechanism for explaining the suppressive properties of the galectin‐1 subfamily on inflammatory and autoimmune processes.

Suppression of experimental autoimmune diseases and prolongation of allograft survival by treatment of animals with low doses of heparins.

The ability of activated T lymphocytes to penetrate the extracellular matrix and migrate to target tissues was found to be related to expression of a heparanase enzyme (Naparstek, Y., I. R. Cohen, Z. Fuks, and I. Vlodavsky. 1984. Nature (Lond.). 310:241-243; Savion, N., Z. Fuks, and I. Vlodavsky. 1984. J. Cell. Physiol. 118:169-176; Fridman, R., O. Lider, Y. Naparstek, Z. Fuks, I. Vlodavsky, and I. R. Cohen. 1987. J. Cell. Physiol. 130:85-92; Lider, O., J. Mekori, I. Vlodavsky, E. Baharav, Y. Naparstek, and I. R. Cohen, manuscript submitted for publication). We found previously that heparin molecules inhibited expression of T lymphocyte heparanase activity in vitro and in vivo, and administration of a low dose of heparin in mice inhibited lymphocyte traffic and delayed-type hypersensitivity reactions (Lider, O., J. Mekori, I. Vlodavsky, E. Baharav, Y. Naparstek, and I. R. Cohen, manuscript submitted for publication). We now report that treatment with commercial or chemically modified heparins at relatively low doses once daily (5 micrograms for mice and 20 micrograms for rats) led to inhibition of allograft rejection and the experimental autoimmune diseases adjuvant arthritis and experimental autoimmune encephalomyelitis. Higher doses of the heparins were less effective. The ability of chemically modified heparins to inhibit these immune reactions was associated with their ability to inhibit expression of T lymphocyte heparanase. There was no relationship to anticoagulant activity. Thus heparins devoid of anticoagulant activity can be effective in regulating immune reactions when used at appropriate doses.

Physically damaged extracellular matrix induces TNF-alpha secretion by interacting resting CD4+ T cells and macrophages.

T lymphocytes and macrophages (Mø) are seen to accumulate at sites of lesions in blood vessel walls, suggesting that these cells may contribute to the initiation of the local inflammatory reaction. Tumour necrosis factor‐α (TNF‐α), a cytokine produced by both cell types, plays a major role in inflammatory reactions, in blood vessel formation, in thrombosis and in atherosclerosis. We now report that secretion of TNF‐α by CD4+ T cells and Mø can be induced in vitro in the absence of antigen, in an MHC‐II‐independent manner by immobilized extracellular matrix (ECM), Moreover, the level of TNF secretion is greatly enhanced in the presence of physically damaged ECM (dECM), This mode of TNF secretion is regulated primarily by the fibronectin or laminin glycoprotein components of ECM, Thus, a multicellular interaction with ECM proteins exposed as a consequence of vascular wall injury can serve to signal the secretion of TNF‐α by both cell types which induces the recruitment of additional immune cells to the developing lesion.

Intravenous gammaglobulin treatment in multiple sclerosis and experimental autoimmune encephalomyelitis: delineation of usage and mode of action.

Multiple sclerosis (MS) is a central nervous system demyelinating disease of implicated autoimmune aetiology. The effect was evaluated of intravenous gammaglobulin (IVIg), a successful therapy in various autoimmune diseases, in relapsing-remitting MS patients treated for three years. IVIg treatment significantly reduced the number and severity of acute exacerbations and resulted in a lesser neurological disability. There were no significant short or long-term adverse effects to IVIg treatment. To clarify the putative therapeutic effects of IVIg, this treatment was examined in the animal model of experimental autoimmune encephalomyelitis (EAE) in the rat. IVIg suppressed active EAE in relation to disease severity and duration, despite the presence of T-cell reactivity to specific antigens, while the treatment had no effect on passive EAE induced by adoptive transfer of myelin basic protein specific CD4 + T-cells. It is concluded that IVIg treatment may be a promising treatment in relapsing-remitting MS as it can alter the natural course of the disease.

Disaccharides generated from heparan sulphate or heparin modulate chemokine-induced T-cell adhesion to extracellular matrix.

We have found previously that disaccharides (DS) enzymatically generated from heparin or heparan sulphate can modulate tumour necrosis factor‐α (TNF‐α) secretion from immune cells in vitro and cell‐mediated immune reactions in vivo. Here, we show that such DS can modulate the adhesion and migration of human T cells. We found that certain heparin‐ and heparan sulphate‐derived DS induced, in a dose‐dependent manner, the adhesion of human T cells to both extracellular matrix (ECM) and immobilized fibronectin (FN); maximal T‐cell adhesion occurred with 1 ng/ml of DS. The levels of T‐cell adhesion to ECM that were induced by the tested DS molecules resembled those induced by the prototypic chemokine, macrophage inflammatory protein 1β (MIP‐1β). However, the kinetics of DS‐induced T‐cell adhesion to FN resembled that induced by phorbol myristate acetate (PMA), but not that induced by MIP‐1β. This adhesion appeared to involve β1 integrin recognition and activation, and was associated with specific intracellular activation pathways. Although a first exposure of T cells to certain DS molecules appeared to result in cell adhesion, a subsequent exposure of T cells to pro‐adhesive chemokines, such as MIP‐1β or RANTES, but not to other pro‐adhesive stimuli, for example interleukin‐2 or CD3 cross‐linking, resulted in inhibition of T‐cell adhesion to and chemotactic migration through FN. Hence, we propose that the breakdown products of tissues generated by inflammatory enzymes are part of an intrinsic functional programme, and not necessarily molecular waste. Moreover, because the DS molecules exert their modulatory functions within a limited time, it appears that the historical encounters of the tissue‐invading cells with the constituents of inflamed loci may dictate the cells’ behaviour upon subsequent exposure to proinflammatory mediators.