PRIOR CONCURRENT THERAPY: Biologic therapy: Prior stem cell transplantation allowed At least 4 weeks since prior biologic therapy No other concurrent immunotherapy Chemotherapy: At least 4 weeks since prior chemotherapy No concurrent chemotherapy Endocrine therapy: At least 4 weeks since prior endocrine therapy No concurrent hormonal therapy (except contraceptives and replacement steroids) No concurrent corticosteroids Radiotherapy: See Disease Characteristics At least 4 weeks since prior radiotherapy for localized disease No concurrent radiotherapy Surgery: Not specified Other: No other concurrent experimental medications (including approved drugs tested in an investigational setting)