Only high-affinity receptors for interleukin 2 mediate internalization of ligand.
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.
Weissman
A M
AM
Harford
J B
JB
Svetlik
P B
PB
Leonard
W L
WL
Depper
J M
JM
Waldmann
T A
TA
Greene
W C
WC
Klausner
R D
RD
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
D000911:Antibodies, Monoclonal; D000936:Antigen-Antibody Complex; D007376:Interleukin-2; D011971:Receptors, Immunologic; D015375:Receptors, Interleukin-2