Interleukin-15 interactions with interleukin-15 receptor complexes: Characterization and species specificity

Interleukin (IL-) 2 and IL-15 share the IL-2 receptor betagamma(c) subunits (IL-2Rbetagamma(c)) but have specific, unique a receptor subunits. We studied species specificity of human (hu), simian (si), and mouse (mu) IL-15 and found that hu and A IL-15 behaved similarly in all systems investigated. Hu and mu IL-15 bound hu or mu IL-15Ralpha with equal high affinity in the presence or absence of IL-2Rbetagamma(c), and exhibited similar proliferative activities on cells containing all three subunits. However, quantitative differences were noted in the specific activity of hu and mu IL-15 in both in vitro and in vivo systems utilizing IL-2Rbetagamma(c) in the absence of IL-15Ralpha. These data show that hu IL-15 may be used in mouse model systems, however care must be taken when comparing the efficacy and toxicity of cytokines across species. (C) 2002 Elsevier science Ltd. All rights reserved.