TRIM21 and familial long QT syndrome: 1. acute inhibition in HEK293-hERG cells and/or guinea-pig ventricular myocytes incubated with sera/purified IgGs/affinity-purified anti-Ro/SSA-52kD antibodies from anti-Ro/SSA-positive CTD patients with LQTS 2. acute inhibition in HEK293-hERG cells incubated with anti-Ro/SSA-positive sera from Ro52kD-immunized guinea-pigs