Turning 'sweet' on immunity: galectin–glycan interactions in immune tolerance and inflammation

This Review discusses the importance of galectin-glycan interactions in regulating T cell survival, activation, cytokine production and regulatory functions, as well as shaping the B cell compartment. Targeting these interactions could have important therapeutic implications for inflammation, autoimmunity and cancer. The function of deciphering the biological information encoded by the glycome, which is the entire repertoire of complex sugar structures expressed by cells and tissues, is assigned in part to endogenous glycan-binding proteins or lectins. Galectins, a family of animal lectins that bind N-acetyllactosamine-containing glycans, have many roles in diverse immune cell processes, including those relevant to pathogen recognition, shaping the course of adaptive immune responses and fine-tuning the inflammatory response. How do galectins translate glycan-encoded information into tolerogenic or inflammatory cell programmes? An improved understanding of the mechanisms underlying these functions will provide further opportunities for developing new therapies based on the immunoregulatory properties of this multifaceted protein family.