The human interleukin 2 receptor beta chain (p70). Direct identification, partial purification, and patterns of expression on peripheral blood mononuclear cells

IL-2 binds to high- and low-affinity receptors on activated T cells. The high-affinity receptor was hypothesized to consist of the noncovalent association between the alpha chain (IL-2-R-alpha, p55) and a beta chain (IL-2-R-beta, p70), whereas the low-affinity receptor consists of p55 without p70. We now directly identify p70 as a 65-77-kD glycoprotein doublet. Preparative quantities of the IL-2/p70 complex have been isolated. Further, we demonstrate that p70 is the principal IL-2 binding protein on both resting CD4+ and CD8+ T cells and that both p70 and p55 can be induced on normal B cells and monocytes.