With regard to B cell-directed therapies, belimumab, a monoclonal antibody (mAb) against the B cell activating factor (BAFF), was approved by the FDA firstly as a biologic for adult (2011) and pediatric (2019) SLE patients [46,47,48] and additionally for adult (2020) and pediatric (2022) LN patients [47]. This evidence concerns the gene TNFSF13B and systemic lupus erythematosus.