title: Only high-affinity receptors for interleukin 2 mediate internalization of ligand.
abstract: Interleukin 2 (IL-2) receptors are expressed on activated T cells and in select T-cell leukemias. Recently, it has been demonstrated that at least two classes of receptor for IL-2 exist with markedly different affinities for ligand. All known biological actions of IL-2 have been correlated with occupancy of high-affinity sites; the function of the low-affinity sites remains unknown. Receptor-mediated endocytosis is the primary means of internalization of cell-surface receptors and their ligands. The internalization of IL-2 bound to high- and low-affinity receptor sites was studied in a human T-cell lymphotrophic virus type 1 (HTLV-1)-infected human T-cell leukemia cell line and in a cloned murine cytotoxic T-cell line (CTLL). Internalization of IL-2 occurred only when bound to high-affinity sites. In addition, an anti-receptor antibody (anti-Tac), which binds equally well to high- and low-affinity sites, demonstrated no detectable internalization. The implications of these findings as they relate to IL-2 receptor structure and function are discussed.
authors.forename: A M
authors.initials: AM
authors.lastname: Weissman
authors.forename: J B
authors.initials: JB
authors.lastname: Harford
authors.forename: P B
authors.initials: PB
authors.lastname: Svetlik
authors.forename: W L
authors.initials: WL
authors.lastname: Leonard
authors.forename: J M
authors.initials: JM
authors.lastname: Depper
authors.forename: T A
authors.initials: TA
authors.lastname: Waldmann
authors.forename: W C
authors.initials: WC
authors.lastname: Greene
authors.forename: R D
authors.initials: RD
authors.lastname: Klausner
mesh_terms: D000911:Antibodies, Monoclonal / Q000276:immunology; D000936:Antigen-Antibody Complex; D004705:Endocytosis; D006801:Humans; D007376:Interleukin-2 / Q000378:metabolism*; D011971:Receptors, Immunologic / Q000276:immunology / Q000378:metabolism*; D015375:Receptors, Interleukin-2
chemical_list: D000911:Antibodies, Monoclonal; D000936:Antigen-Antibody Complex; D007376:Interleukin-2; D011971:Receptors, Immunologic; D015375:Receptors, Interleukin-2