KTX-Sp2 is a potassium channel toxin. KTX-Sp2 effectively blocks three types of exogenous voltage-gated potassium channels: Kv1.1, Kv1.2 and Kv1.3. Ktx-Sp2 inhibits endogenous Kv1.3 and suppresses Ca 2+ signaling in Jurkat T cells. Ktx-Sp2 inhibits IL-2 secretion from activated Jurkat T cells.