TRIM21 and systemic lupus erythematosus: By combining the analysis of an RNA-Seq data set of peripheral blood SLE leukocytes, epitope mapping with commercial anti-Ro52 antibodies, and the study of a large cohort of patients with SLE, we further concluded that the large majority of antibodies to Ro52 in SLE are directed against an epitope encoded by exon 4 in TRIM21 — found in Ro52α and Ro52γ — which is the major target of anti-Ro52 antibodies in in vivo IFN-activated SLE neutrophils.