Very few diseases are directly caused by ion channel mutations, yet many drugs for various diseases work by modulating ion channel activity. This is because ion channels are cellular “gatekeepers,” monitoring intracellular concentrations of Na+ , Ca+ , K+ , or Cl− to control cardiac pacemaking, membrane potential, neurotransmitter release, hormone secretion, cell proliferation, cell volume regulation, and lymphocyte differentiation. One ion channel that controls lymphocyte differentiation is the highly T cell specific Kv1.3 channel. Since the discovery of Kv1.3 channels in Tc cells, these lymphocyte channels have been targeted in developing immunomodulatory drugs that might exhibit lower toxicities than those currently in use (1 ,2 ).
