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.