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 inter leukin-2 (IL-2) to its receptor (IL-2R beta) induces IL-2R beta phosph orylation by the tyrosine kinase p56(lek) associated with the T-cell r eceptor (TCR) complex, we investigated the possibility that this mecha nism was due to the putative lectin activity of IL-2 ([Sherblom, Sathy amoorthy, Decker and Muchmore (1989) J. Immunol, 143, 939-944]. Here w e demonstrate that IL-2 is a calcium-independent lectin specific for o ligomannosidic N-glycans with five and six mannose residues, This lect in activity is preserved after binding of IL-2 to IL-2R beta. IL-2 beh aves as a bifunctional molecule that associates IL-2R beta with specif ic glycoprotein ligands of the TCR complex including a glycosylated fo rm of CD3.