Two major issues severely limit the studies of human recombinant cytokines/growth factors in nonhuman primates. First, assays and reagents specific for the detection and quantitation of human cytokines do not all function when utilized to detect/quantitate the nonhuman primate cytokines. Second, although most of the human cytokines appear to induce similar, if not identical, biologic function when used with cells from nonhuman primates in vitro or in vivo, they invariably induce Ab responses in vivo, precluding their repeated and/or continued use in vivo. Our laboratory has thus initiated studies to clone, sequence, and prepare recombinant cytokines from nonhuman primates and to define assays and reagents for their detection and quantitation at the nucleic acid and protein level. The data that were derived from such studies show that the nonhuman primate cytokines IL-1 alpha, IL-1 beta, IL-2, IL-4, IL-5, IL-6, IL-8, IL-10, IL-12 alpha, IL-12 beta, IL-15, IFN-alpha, IFN-gamma, and TNF-alpha share 93 to 99% homology at the nucleic acid and protein level with the human equivalents. The most prominent differences between human and nonhuman primate cytokine sequences were noted for IL-1 alpha/beta, IL-2, IL-8, IFN-alpha, IFN-gamma, and IL-12 beta. The aligned sequences of cytokines for human and several nonhuman primate species are provided herein, and a phylogenetic analysis of the published sequences of select cytokines from other species, along with those of the nonhuman primates, are described. In addition, comparative analysis of the relative bioactivity of our immunoaffinity-purified recombinant rhesus macaque IL-4, IL-15, and IFN-gamma with commercially available human recombinant cytokines is described herein.