TRIM21 and mixed connective tissue disease: Serum samples from 110 patients with SLE, 118 patients with SS, 41 patients with MCTD, and 73 controls were analysed by ELISA for IgE autoantibodies against dsDNA, SSA/Ro52, and SSA/Ro60, SSB/La, and RNP proteins using recombinant antigens.