Interestingly, a protection against de novo renal SLE conferred from 1 mg/kg i.v. (HR: 0.38; 95% CI: 0.20–0.73) and 200 mg s.c. (HR: 0.69; 95% CI: 0.54–0.88) but not 10 mg/kg i.v. belimumab was demonstrated in patients with SLE and no prior nephritis history [43], which along with real-world observations of nephritis occurrence in SLE patients under treatment [100,101] and documentation of rapid reductions in IL-10 levels upon belimumab treatment commencement [102] has resulted in speculations about effects of belimumab on B cells with regulatory properties [43,46]. Here, IL10 is linked to systemic lupus erythematosus.