TRIM21 and familial long QT syndrome: Specifically, our group demonstrated that incubation of human embryonic kidney-293 cells stably expressing the hERG-K+-channel (HEK293-hERG) or guinea-pig ventricular myocytes with serum, purified IgGs, or affinity-purified anti-Ro/SSA-52kD obtained from CTD patients with LQTS was associated with an acute (minutes), concentration-dependent and reversible IKr inhibition (23).