PRIOR CONCURRENT THERAPY: Biologic therapy: At least 12 months since prior rituximab No prior interleukin-12 No other concurrent immunotherapy Chemotherapy: See Disease Characteristics No prior fludarabine or 2-chlorodeoxyadenosine unless CD4 count normal Recovered from prior chemotherapy No concurrent chemotherapy Endocrine therapy: No concurrent steroid therapy Radiotherapy: No concurrent radiotherapy Surgery: Not specified