Anti-Tac for Treatment of Leukemia

* ELIGIBILITY CRITERIA: * Population Base. * Patients diagnosed with smoldering or chronic human T-lymphotropic virus type 1 (HTLV-I)- associated adult T-cell leukemia. INCLUSION CRITERIA: * Patients must have serum antibodies directed to HTLV-I. * All patients must have a histologically confirmed diagnosis of adult T-cell leukemia/lymphoma. * At least 5 percent of each patient's peripheral blood, lymph node, pulmonary or dermal malignant cells must react with the anti-Tac mAb as determined by immunofluorescent staining or, alternatively, the serum-soluble interleukin 2 (IL-2) receptor levels must be greater than 1,000 units/ml (normal geometric mean, 235; with a 95% confidence interval of 112 to 502 units/mL). * Smoldering or chronic stage Tac-expressing adult T-cell leukemia defined by the Shimomyama Criteria (37) are eligible. * To be diagnosed as smoldering Adult T-cell Leukemia (ATL), the patient must have a normal lymphocyte count (less than 4 times 10\^3/mm\^3), less than or equal to 5 percent abnormal lymphocytes on morphologic examination of the peripheral blood smear or on fluorescence activated cell sorting (FACS) analysis (cells with a homogenous staining pattern and a greater than 1 log increase in the magnitude of fluorescence emission of the anti-Tac peak over background expression), * no hypercalcemia, * lactate dehydrogenase less than or equal to 1.5 times the upper limit of normal, * no lymphadenopathy, * no involvement of extra nodal organs except skin or lung and no malignant pleural effusion or ascites. * If the abnormal lymphocyte count is less than 5 percent, the patient must have at least one histologically proven skin ATL lesion to be diagnosed as smoldering ATL. * Patients with \>5% of circulating lymphocytes that are abnormal are considered to have measurable disease. * The patient must have a granulocyte count of at least 500/mm\^3 and a platelet count of 25,000/mm\^3. * Patients must have a creatinine of less than 3.0 mg/dl. * Patients must have a Karnofsky performance score of greater than 60 percent. * ATL patients without, as well as those with, previous chemotherapy will be eligible for inclusion in the study. * Patients with previous therapy with a monoclonal antibody including anti-Tac will be eligible for the study provided that they do not have a positive HAHA (human antibody to humanized anti-Tac) value (i.e., such patients must have a value greater than 250 ng/ml). * Omission of cytotoxic chemotherapy for ATL for 3 weeks prior to entry into the trial is required. * However, patients receiving corticosteroids will not be excluded. * Patients must have a life expectancy of greater than 2 months. * Eligible patients must be greater than or equal to 10 years old. * There is no upper age limit. * Patients over the age of 18 years must be able to understand and sign an Informed Consent form. * Eligible minors greater than or equal to 10 years old must give assent to participate in this study. EXCLUSION CRITERIA: * Patients with symptomatic central nervous system disease that is due to the adult T-cell leukemia will be excluded. * However, patients that have both ATL and another HTLV-I-associated disease, tropical spastic paraparesis (TSP), will be included. * Furthermore, Tac-expressing T cells may be present in the cerebrospinal fluid (CSF) as long as the patient does not have symptomatic central nervous system (CNS) disease. * Pregnant and/or nursing patients are not eligible for the study. * Human immunodeficiency virus (HIV) positive patients are excluded from the study. * Patients with serum glutamic oxaloacetic transaminase (SGOT) or serum glutamic pyruvic transaminase (SGPT) values 5.0-fold greater than the upper limit of normal or bilirubin greater than 2.9 mg/dl will be excluded. * If a liver function test is judged to be elevated due to the underlying ATL, this parameter will be considered an unevaluable parameter for toxicity determinations. * Acute or Lymphoma stage HTLV-1 associated adult T cell leukemia.