Lectin activities of cytokines: A new concept in immunology

Abstract

Several cytokines were described as having carbohydrate-binding (lectin) properties. A fine analysis of their high affinity ligands indicated that the specificity is directed against glycans that are generally rare in normal tissues. These lectin activities open new concepts in immunology because it modifies our understanding of their mechanism of action. The carbohydrate-recognition domain of the cytokines makes these molecules bifunctional. Consequently, the expression of the biological activity of the cytokine relies on its carbohydrate-binding activity, which allows the specific association of the cytokine receptor with molecular complexes comprising the specific kinase/phosphatase involved in receptor phosphorylation/dephosphorylation and in specific signal transduction. Correlatedly, a cytokine can act only on cells possessing both the receptor and the ligand, the latter being in the case of IL-2 and IL-6 a glycoprotein molecule considered as a receptor. Based on a few examples, it is suggested that molecular modeling of the lower energy conformation of the high affinity ligands of the cytokine and computational docking of these conformers into the 3D-structure of the cytokine are able to propose a localization of the carbohydrate-recognition domain.