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

Abstract

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.