TNFSF13 and systemic lupus erythematosus: Based on the association of the BAFF system with renal involvement, the poor renal prognosis for proliferative LN in Latin American SLE patients, and the small number of validated renal biomarkers, this study evaluated the renal tissue expression of BAFF, APRIL, BR3, TACI, and BCMA in patients with proliferative LN.