Interleukin 2 is a lectin that associates its receptor with the T-cell receptor complex

To determine the nature of the mechanism by which the binding of interleukin-2 (IL-2) to its receptor (IL-2R beta) induces IL-2R beta phosphorylation by the tyrosine kinase p56lck associated with the T-cell receptor (TCR) complex, we investigated the possibility that this mechanism was due to the putative lectin activity of IL-2 ([Sherblom, Sathyamoorthy, Decker and Muchmore (1989) J. Immunol. 143, 939-944]. Here we demonstrate that IL-2 is a calcium-independent lectin specific for oligomannosidic N-glycans with five and six mannose residues. This lectin activity is preserved after binding of IL-2 to IL-2R beta. IL-2 behaves as a bifunctional molecule that associates IL-2R beta with specific glycoprotein ligands of the TCR complex including a glycosylated form of CD3.