Fig. 4. "Window" Kv1.3 current in B and T cells. Window current corresponds to the fraction of unitary current through a Kv1.3 channel, which, with a certain probability, is activated by voltage and remains non-inactivated at steady state. It is a product of voltage dependent steady state open probability, multiplied by unitary current through an open Kv1.3 channel at the same voltage. Steady state open probability was calculated as a product of respective values, taken from activation and inactivation curves (see Fig. 1. B for an example) at given voltage. Arrowheads indicate mean cell resting potential values for each condition, directly measured by clamping membrane current to zero, I=0 mode. SE in all cases was about the symbol size, <2.5 mV, omitted for clarity.