Together with the previous papers, these results suggest that TRIM21 negatively regulates the expression of IRF5 protein, decreases IRF4 expression, and thereby induces both BLIMP-1 suppression and BCL-6 expression, resulting in suppression of aberrant B-cell differentiation and Ab overproduction during lupus-like pathological condition. Here, IRF4 is linked to systemic lupus erythematosus.