High B-cell activating factor is not associated with worse 3-year graft outcome in blood group-incompatible kidney transplantation with rituximab induction

B cells and their regulation by B-cell activating factor BAFF are of growing interest in kidney transplantation (KTx). There is evidence that high serum (s) BAFF leads to increased allosensitization and impaired long-term graft function. We prospectively investigated sBAFF, peripheral blood lymphocytes (PBL), and donor-specific HLA antibodies (DSA) in patients after ABOi with B-cell depleting rituximab induction treatment and compared them to a group of blood group-compatible (ABOc) living donor kidney recipients. Twelve patients after ABOi and 18 after ABOc were included. After rituximab treatment prior to ABOi, B cells remained significantly lower 1year after KTx (1.2% (0.0-17.8) compared to ABOc of 8.6% (2.8-35.0), p=0.0004, and also BAFF-R expression was significantly lower in ABOi (p<0.006). sBAFF remained elevated 1year post-Tx compared to ABOc (3615 +/- 1800 vs. 1394 +/- 493pg/mL, p<0.004). Kidney function was not significantly different between both groups after 1, 2, and 3years. The use of rituximab in ABOi together with maintenance immunosuppression leads to significant elevation of sBAFF and lowering of B-cell numbers for more than 1year, and this does not correlate with worse 3-year graft outcome.