Through a combination of fluorescence microscopy and patch-clamp analysis we have identified a striking alteration in K+ channel expression in terminally differentiated human CCR7-CD45RA-effector memory T lymphocytes (TEM). Following activation, TEM cells expressed significantly higher levels of the voltage-gated K+ channel Kv1.3 and lower levels of the calcium-activated K+ channel IKCA1 than naive and central memory T cells (TCM). Upon repeated in vitro antigenic stimulation, naive cells differentiated into Kv1.3 highIKCa1low TEM cells, and the potent Kv1.3-blocking sea anemone Stichodactyla helianthus peptide (ShK) suppressed proliferation of TEM cells without affecting naive or TCM lymphocytes. Thus, the Kv1.3highIKCa1low phenotype is a functional marker of activated TEM lymphocytes. Activated myelin-reactive T cells from patients with MS exhibited the Kv1.3 highIKCa1low TEM phenotype, suggesting that they have undergone repeated stimulation during the course of disease; these cells may contribute to disease pathogenesis due to their ability to home to inflamed tissues and exhibit immediate effector function. The Kv1.3 highIKCa1low phenotype was not seen in glutamic acid decarboxylase, insulin-peptide or ovalbumin-specific and mitogen-activated T cells from MS patients, or in myelin-specific T cells from healthy controls. Selective targeting of Kv1.3 in TEM cells may therefore hold therapeutic promise for MS and other T cell-mediated autoimmune diseases.
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