Proleukin in Combination With Rituxan in Patients With Low-Grade Non-Hodgkin's Lymphoma Who Have Previously Failed Rituxan Treatments

Diagnosis and disease status: * Subjects with CD20+, B-cell, Non-Hodgkin's lymphoma of low-grade or follicular histology with measurable relapsed or unresponsive disease after prior therapy; mantle cell and chronic lymphocytic leukemia subtypes are excluded. * Subjects who previously received a single-agent course of rituximab and showed no tumor response, or had a response lasting \< 6 months. The previously administered rituximab must have included at least 75% of the standard 4-week regimen (4 x 375 mg/m2). A record of the previous rituximab treatment and response must be available as a source document at the site. Exclusion: * Subjects who showed no tumor response or a response lasting \<6 months to treatment with Rituximab in combination with Chemotherapy or another therapeutic modality (radiation or radioimmunoconjugates). * HIV positive. * Symptomatic thyroid disease requiring medical intervention other than replacement treatment for hypothyroidism. * Clinically significant cardiac, pulmonary, and /or hepatic dysfunction (if subject has history of congestive heart failure or myocardial infarction, must have been stable for at least 6 months, and have no current symptoms * If cardiac ejection fraction has been measured, it must be greater than 50%.