TRIM21 and systemic lupus erythematosus: In this study, the serous levels of ANA, anti-dsDNA and anti-ENA, including anti-SSA, anti-SSB, anti-Ro52, anti-Sm, anti-nRNP/Sm, anti-rRNP, and anti-nucleosome, the hallmark antibodies of SLE, were first determined and analyzed for their relationship with the frequency of PD-L1-expressing neutrophils.