Rituximab and Denileukin Diftitox in Treating Patients With Previously Untreated Stage III or Stage IV Follicular B-Cell Non-Hodgkin's Lymphoma

OBJECTIVES: Primary * Determine the response rate (complete response \[CR\], unconfirmed CR, and partial response) in patients with previously untreated stage III or IV follicular B-cell non-Hodgkin's lymphoma treated with rituximab and denileukin diftitox. * Assess the overall survival, time-to-progression, duration of response, and time-to-new therapy in patients treated with this regimen. Secondary * Determine whether this regimen depletes or inhibits the function of regulatory T cells in these patients. OUTLINE: This is a multicenter study. Patients receive rituximab IV on days 1, 8, 15, and 22. Patients also receive denileukin diftitox IV over 15-60 minutes on days 1-5. Treatment with denileukin diftitox repeats every 21 days for up to 4 courses in the absence of disease progression or unacceptable toxicity. Blood is collected at baseline; on day 1 of courses 2-4; and 1 and 4 months after completion of study treatment for research studies. Research studies include analysis of peripheral blood lymphocyte subsets expressing CD3, CD4, CD8, CD19, CD25, and CD26 by flow cytometry; quantitation of CD4+, CD25+ regulatory T cells by flow cytometry; tumor-specific γ-interferon-secreting T cells by enzyme-linked immunospot assay; tumor-specific cytotoxic T-lymphocyte activity; and immune activation by enzyme-linked immunosorbent assay. After completion of study treatment, patients are followed periodically for up to 5 years after registration. PROJECTED ACCRUAL: A total of 53 patients will be accrued for this study.