PRIOR CONCURRENT THERAPY: Biologic therapy: See Disease Characteristics No prior denileukin diftitox (DAB389-interleukin-2) or DAB486-interleukin-2 No concurrent interferon Chemotherapy: No concurrent chemotherapy* No concurrent extracorporeal photochemotherapy* No concurrent systemic or combination cytotoxic chemotherapy No concurrent topical chemotherapy *For remission induction of CTCL Endocrine therapy: No other concurrent corticosteroids Radiotherapy: No concurrent electron beam radiotherapy and/or photophoresis Surgery: Not specified Other: At least 21 days since any prior anticancer therapy and recovered No other concurrent anticancer therapy for CTCL No concurrent experimental drugs or approved drugs tested in an investigational setting No concurrent topical therapy* No concurrent phototherapy* No concurrent cyclosporine No concurrent systemic retinoids *For remission induction of CTCL