Inclusion Criteria:

- CD20+ follicular B-cell non-hodgkin’s lymphoma with at least 1 site of measurable
disease.

- Previous treatment with 1 to 4 prior chemotherapy regimens

- ECOG performance status of greater than or equal to 2

- Life expectancy of greater than 18 weeks

- Meet safety lab requirements and organ function tests

Exclusion Criteria:

- Prior treatment with rituximab or IL-2

- Prior radioimmunotherapy including Zevalin or Bexxar

- 5 or more prior chemotherapy regimens

- Clinically significant cardiac disease, lung dysfunction, autoimmune disease, thyroid
disease, active infection, unstable psychiatric condition, or HIV infection.

- History of allogenic bone marrow transplant

- Female subjects that are pregnant or breast feeding

- Immunosuppressive therapy including corticosteroids or investigational agents within
4 weeks prior to the planned start of study treatment