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 1 year 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 1 year post-Tx compared to ABOc (3615 ± 1800 vs. 1394 ± 493 pg/mL, p < 0.004). Kidney function was not significantly different between both groups after 1, 2, and 3 years. 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 1 year, and this does not correlate with worse 3-year graft outcome.