Constitutive expression of high affinity interleukin 2 receptors on human CD16-natural killer cells in vivo.

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Abstract
The majority of human NK cells express low affinity IgG Fc receptors (CD16+), whereas a minor subset of NK cells lack Fc receptor expression (CD16-). In contrast to CD16+ NK cells that express only p75 IL-2 receptors. CD16- NK cells constitutively co-express both p75 and p55 IL-2 receptors in vivo and preferentially respond to low concentrations of IL-2 with increased cytolytic activation and proliferation. Scatchard analysis demonstrated the presence of .apprx.1,2000 high affinity (.apprx.25 pM kD) and .apprx.9,600 intermediate affinity (.apprx.2 nM kD) IL-2 receptors on CD16- NK cells. CD16+ NK cells expressed only a single intermediate affinity IL-2 receptor of .apprx.1.9 nM kD (.apprx.9,000 sites per cell). The IL-2 binding data thus substantiated the phenotypic and functional studies and definitively show that the differential responsiveness of CD16- and CD16+ NK cells to IL-2 is manifested through different affinity IL-2 receptors.