TRIM21 and systemic lupus erythematosus: On the other hand, immune serology for lupus markers revealed positive anti-SS-A native (60 kDa) (Ro/SSA), 34 U/ml (<10 U/ml), anti-SSA (Ro-52 recombinant), 44 U/ml (<10 U/ml), and anti-ribosomal P antibodies, 63 U/ml (<10 U/ml), as well as low complement C4, 0.064 (0.20–0.65 g/l), whereas anti-La/SSB, Sm, dsDNA, RNP, anti-histone, anti-cyclic citrullinated peptide, anti-phospholipid antibodies, rheumatoid factor (RF), and immunofluorescence antinuclear antibody (ANA) test (HEp-2 substrate) were all negative.