Inclusion Criteria

DISEASE CHARACTERISTICS:

- Pathologically confirmed follicular B-cell non-Hodgkin's lymphoma (NHL)

- Stage III or IV disease

- Grade 1 or 2 disease

- Previously untreated disease

- Measurable disease, defined as ≥ 1 unidimensionally measurable lesion ≥ 20 mm by
conventional techniques

- Clearly defined bidimensional diameter ≥ 2 x 2 cm on physical examination OR >
2.0 cm in 1 of the dimensions by CT scan, MRI, or plain radiograph imaging

- Splenic enlargement may be used as a measurable parameter if the spleen is
palpable ≥ 3 cm below the left costal margin

- Circulating tumor cells < 5,000/mm³

- Must have paraffin-embedded tissue blocks/slides available

- No CNS lymphoma

PATIENT CHARACTERISTICS:

- ECOG performance status 0-2

- Life expectancy ≥ 1 year

- WBC ≥ 3,400/mm³

- Platelet count ≥ 100,000/mm³

- Hemoglobin ≥ 10.0 g/dL

- Bilirubin ≤ 1.5 times upper limit of normal (ULN)

- Alkaline phosphatase ≤ 3 times ULN

- AST ≤ 3 times ULN

- Creatinine ≤ 1.5 times ULN

- Albumin ≥ 3 g/dL

- Not pregnant or nursing

- Negative pregnancy test

- Fertile patients must use effective contraception during and for 1 year after
completion of study therapy

- No HIV infection

- No other active malignancies

- No active uncontrolled infection

- No known hypersensitivity to denileukin diftitox or any of its components, including
diphtheria toxin, aldesleukin, or excipients

PRIOR CONCURRENT THERAPY:

- No prior chemotherapy, immunotherapy, vaccines, or radiotherapy for NHL