Clinical studies have reported that nuclear antigens such as U1-RNP70, SmD1, histones, SSA and SSB are recognized by CD4+ T cells in patients with SLE, resulting in cytokine production including interleukin (IL)-17, IL-10 and IFN-γ10–12 (Fig. 1). Here, TRIM21 is linked to systemic lupus erythematosus.