Only high-affinity receptors for interleukin 2 mediate internalization of ligand

Proc Natl Acad Sci U S A. 1986 Mar;83(5):1463-6. doi: 10.1073/pnas.83.5.1463.


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.

MeSH terms

  • Antibodies, Monoclonal / immunology
  • Antigen-Antibody Complex
  • Endocytosis
  • Humans
  • Interleukin-2 / metabolism*
  • Receptors, Immunologic / immunology
  • Receptors, Immunologic / metabolism*
  • Receptors, Interleukin-2


  • Antibodies, Monoclonal
  • Antigen-Antibody Complex
  • Interleukin-2
  • Receptors, Immunologic
  • Receptors, Interleukin-2