Inclusion Criteria

Inclusion:

- Diagnosis: CD20+ B-cell non-Hodgkin's lymphoma (NHL) classified as intermediate- or
high-grade according to the Working Formulation, subtypes D to H. Must have
measureable progressive or refractory disease after no more than three prior
chemotherapy regimens.

Exclusion:

- Clinically significant cardiac dysfunction, or a history of myocardial infarction or
heart failure within 6 months of first study treatment

- Clinically significant pulmonary dysfunction.

- Liver disease (note hepatitis C seropositive subjects may be enrolled if they have no
active disease as demonstrated by undetectable HCV viral loads, biopsy showing no
active disease, and/or history of normal transaminases on at least three different
dates within one year of first study treatment).

- Symptomatic thyroid disease requiring medical intervention other than replacement
treatment for hypothyroidism.

- History of autoimmune disease.

- History of positive serology for human immunodeficiency virus (HIV).