The expression of IL-2 and IL-15 mRNA was evaluated in the PBMCs from 6 patients with LGL. There was either no or only minimal IL-2 and IL-15 mRNA expression observed in the patients examined. This contrasts with the high IL-15 expression in the adult T-cell leukemia/lymphoma cell line HuT-102 or in normal PBMCs after ionomycin/phorbol 12-myristate 13-acetate addition.