NK White Blood Cells and Interleukin in Children and Young Adults With Advanced Solid Tumors

* INCLUSION CRITERIA: * Diagnosis: * Histologically confirmed solid tumors, including primary brain tumors. In subjects with brain stem or optic gliomas the requirement for histological confirmation may be waived. * Age: Cohort A: 2 to less than or equal to 29 years old at the time of enrollment. Cohort B: 2 to less than or equal to 25 years old at the time of enrollment. * Patients must have evaluable or measurable malignant disease at enrollment. * Prior Therapy: * The patient s malignancy must have relapsed after or failed to respond to frontline curative therapy and/or there must not be any potentially curative treatment options available at the time of study entry. * There is no limit to the number of prior treatment regimens. However, patients must have fully recovered from the acute toxic effects of all prior chemotherapy, immunotherapy, or radiotherapy prior to study enrollment. Acute toxicity of any previous therapy must have resolved to grade 1 or less, unless specified elsewhere. Myelosuppressive chemotherapy: Patients must not have received myelosuppressive chemotherapy within 3 weeks of enrollment (6 weeks if prior nitrosourea). * Hematopoietic growth factors: At least 7 days must have elapsed since the completion of therapy with a growth factor. At least 14 days must have elapsed after receiving pegfilgrastim. * Biologic (anti-neoplastic agent) or metronomic non-myelosuppressive chemotherapy: At least 7 days must have elapsed since the completion of therapy with a biologic agent. For agents that have known adverse events occurring beyond 7 days after administration, this period prior to enrollment must be extended beyond the time during which adverse events are known to occur. * Monoclonal antibodies: At least 4 weeks must have elapsed since prior therapy that included a monoclonal antibody. * Radiotherapy: 3 weeks must have elapsed since XRT * Performance status: ECOG 0, 1 or 2, or for children less than or equal to10 years of age, Lansky greater than or equal to 60. Note: Patients who are unable to walk because of paralysis, but who are up in a wheelchair, will be considered ambulatory for the purpose of assessing the performance score. * Cardiac function: Left ventricular ejection fraction greater than or equal to 45% or fractional shortening greater than or equal to28%. * Liver function: Serum total bilirubin \< 2 mg/dl, serum AST and ALT less than or equal to 3 x upper limit of normal. Patients with Gilbert syndrome are excluded from the requirement of a normal bilirubin. (Gilbert syndrome is found in 3-10% of the general population, and is characterized by mild, chronic unconjugated hyperbilirubinemia in the absence of liver disease or overt hemolysis). On cohort B, patients with liver involvement by tumor will not be eligible due to potential confounding risk for hepatotoxicity when rhIL15 is administered. NOTE: adult values will be used for calculating hepatic toxicity on this trial, as is standard on POB phase I trials. \- Renal function: Age-adjusted normal serum creatinine according to the following table or a creatinine clearance greater than or equal to 60 ml/min/1.73 m(2). Age (years) \<TAB\>\<TAB\>\<TAB\>Maximum serum creatinine (mg/dl) less than or equal to5 \<TAB\>\<TAB\>0.8 \>5 less than or equal to 10 \<TAB\> 1.0 \>10 less than or equal to 15 \<TAB\>1.2 \> 15 \<TAB\>\<TAB\>\<TAB\>\<TAB\>1.5 * Marrow function: ANC must be \> 750/mm(3) (unless due to underlying disease in which case there is no grade restriction), platelet count must be greater than or equal to 75,000/mm(3) (not achieved by transfusion). Lymphopenia, CD4 lymphopenia, leukopenia, and anemia will not render patients ineligible. * Female patients (and when relevant their male partners) must be willing to practice birth control (including abstinence) during and for two months after treatment, if of childbearing potential. * Ability to give informed consent. For patients \<18 years of age their legal guardian must give informed consent. Pediatric patients will be included in age-appropriate discussion in order to obtain verbal assent. * Durable power of attorney form offered (patients greater than or equal to18 years of age only). EXCLUSION CRITERIA: * Untreated CNS metastatic disease as defined by: * Solid Tumors: History of untreated metastatic CNS tumor involvement. Extradural masses which have not invaded the brain parenchyma or parameningeal tumors without evidence for leptomeningeal spread will not render the patient ineligible. Patients with previous CNS tumor involvement are eligible IF the CNS tumor(s) has been treated and has been stable or resolving for at least 4 weeks; and if the patient does not currently require steroids. * Prior history allogeneic stem cell transplantation. * Breast feeding or pregnant females (due to risk to fetus or newborn). * HIV or HTLV-I/II (due to unacceptable risk associated with severe immune suppression and risk associated with cell products). * Hepatitis B surface antigen (HBsAg) positive or hepatitis C antibody positive with elevated liver transaminases. All patients with chronic active hepatitis (including those on antiviral therapy) are ineligible. * Patients who require systemic corticosteroid or other systemic immunosuppressive therapy. Immunosuppressive therapy must be stopped at least 28 days prior to enrollment. Topical agents and/or inhaled corticosteroids are permitted. * High risk of inability to comply with therapy in the estimation of the PI. * Clinically significant systemic illness (e.g. serious active infections or significant vital other organ dysfunction), that in the judgment of the PI would likely compromise the patient s ability to tolerate protocol therapy or significantly increase the risk of complications. * Prior history of pericarditis or pericardial effusion. INCLUSION OF WOMEN AND MINORITIES: Both men and women of all races and ethnic groups are eligible for this trial.