- Secondary objectives are: 1) to identify biologically active doses of activated autologous NK cells plus or minus rhIL15 by monitoring changes in NK cell number, phenotype and function, 2) to assess pharmacokinetics and immunogenicity of rhIL15 in a pediatric population, and 3) assess antitumor effects and changes in FDG-PET following administration of activated NK cells to lymphopenic hosts plus or minus rhIL15. 4) to evaluate saftey and efficacy of subsequent cycles of autologous NK cell infusions in patients in cohort A who received benefit from the first NK cell infusion.