Abstract
Some cytokines have a carbohydrate recognition activity which seems to modulate the interaction between cytokines and their receptors in an immune system. In this article, we have given an overview of the studies on cytokine's carbohydrate recognition activity and reviewed the functional roles of IL-2 carbohydrate recognition activity. CTLL-2 cells proliferate dependently on IL-2. Since a high-mannose type glycan with five or six mannosyl residues can inhibit IL-2-dependent cell proliferation and its signal transduction, it was indicated that the high-mannose type glycan functioned as a modulator of IL-2 on T cell proliferation. Since it has been reported that each IL-2 receptor subunit expressed independently shows only weak binding to IL-2, the mechanism by which IL-2 stimulates the formation of a high affinity IL-2-IL-2Rα, -β, or-γ complex remained unclear. However, we found that IL-2 recognizes both the high-mannose type glycan with five or six mannosyl residues on IL-2 receptor α subunit and its specific peptide sequence. The formation of IL-2-IL-2Rα complex via dual recognition may be a trigger to form the high-affinity receptor complex which consists of all constituents required for the cellular signaling.
