KV1.3 belongs to the Shaker family of voltage-dependent K+ channels. The channel is widely expressed in the brain, lung and osteoclasts and in several cell populations of hematopoietic origin. It is in these cells (particularly T lymphocytes) that KV1.3 function has centered a lot of attention. It was found that KV1.3 is the main channel. nResponsible for maintaining the resting potential in quiescent cells and regulating the Ca2+ signaling that is indispensable for normal T lymphocyte activation. nBased on the central role of KV1.3 in regulating the initiation of an immune response, the channel has been recognized as a potential target for immunosuppressant drugs. nThe central role of KV1.3 in immune system cells created a real need for a specific antibody that would be able to work in flow cytometry applications.