Since β1 but not β3b subunits slow the activation kinetics (τAct) of KCa1.1 channels [48], we measured these kinetics in RA-FLS and found a spread in τAct with only 17 (31 %) of the 54 cells assessed having a τAct longer than 4 milliseconds and 69 % of cells having a τAct less than or equal to 4 milliseconds (Fig. 3d). Here, KCNMA1 is linked to rheumatoid arthritis.