A second human interleukin-2 binding protein that may be a component of high-affinity interleukin-2 receptors

Nature. 1987 Jun;327(6122):518-22. doi: 10.1038/327518a0.


Although activated human T and B lymphocytes express both high-affinity and low-affinity membrane receptors for interleukin-2 (IL-2), the structural features that distinguish these receptors have remained unresolved. The high-affinity receptors appear to mediate IL-2 induced T cell growth and internalization of IL-2, whereas no function has yet been ascribed to the low-affinity receptors. The Tac antigen is an IL-2 binding protein of relative molecular mass 55,000 (Mr 55K) that participates in the formation of both high- and low-affinity receptors. But Tac complementary DNA transfection and membrane fusion studies have suggested that additional T-cell components are required to produce high-affinity IL-2 receptors. In this study, we report the identification of a second human IL-2 binding protein that (1) has an Mr of approximately 70K, (2) lacks reactivity with the anti-Tac antibody, (3) binds IL-2 with intermediate affinity and (4) is present on the surface of resting T cells, large granular lymphocytes (natural killer cells), and certain T and B cell lines in the absence of the Tac antigen. Chemical crosslinking of 125I-labelled IL-2 bound to high-affinity IL-2 receptors produces labelling of both the p70 protein and the Tac antigen and the anti-Tac antibody blocks the crosslink detection of both of these proteins. Expression of Tac cDNA in a T cell line expressing the p70 protein, but lacking both Tac and high-affinity receptors, results in the reconstitution of high-affinity IL-2 receptors in these cells. Together, these findings suggest that the high-affinity human IL-2 receptor may be a membrane complex composed of at least the p70 protein and Tac antigen.

MeSH terms

  • Animals
  • B-Lymphocytes / immunology
  • Cell Line
  • Interleukin-2 / metabolism*
  • Kinetics
  • Molecular Weight
  • Receptors, Immunologic / isolation & purification
  • Receptors, Immunologic / metabolism*
  • Receptors, Interleukin-2
  • Recombinant Proteins / immunology
  • Recombinant Proteins / metabolism*
  • T-Lymphocytes / immunology


  • Interleukin-2
  • Receptors, Immunologic
  • Receptors, Interleukin-2
  • Recombinant Proteins