Human T-cell leukemia, CCRF-CEM, produced interleukin (IL)-2 stimulated with phorbol myristate acetate (PMA) and pokeweed mitogen (PWM). In PMA/PWM stimulation, IL-2 production in CCRF-CEM was increased by treatment with kaempferol or quercetin, tea (Camellia sinensis L.) flavonols. In this study, we concluded that (1) flavonols affected the expression of CCRF-CEM surface molecules, (2) CCRF-CEM was activated by flavonols, achieving a state receptive to stimulation, and (3) IL-2 production and mRNA expression were promoted by flavonols.