B-cell activating factor, a predictor of antibody mediated rejection in kidney transplantation recipients.

AIM: Donor-specific antibody (DSA) is a widely-used biomarker for antibody-mediated rejection (ABMR) but correctly indicates only 30-40% of patients with ABMR. Additional biomarkers of ABMR in kidney transplant recipients are needed.

METHODS: All 68 kidney transplanted-recipients enrolled in this study were negative for graft rejection as determined by surveillance-biopsy ELISA at day 7 post-transplantation. Allograft biopsy was then performed at 6 months post-transplantation for subclinical-ABMR detection. Recipients were stratified by pre-transplant DSA and BAFF at day 7 into four groups.

RESULTS: During the study period, 13.2% of the recipients demonstrated subclinical-ABMR at 6 months, without patient with clinical ABMR presentations. Overall mean BAFF at day 7 was 393 pg/mL (95% CI = 316-471 pg/mL). The optimal cut-off value for low vs. high BAFF level was 573 pg/mL, with sensitivity and specificity at 77.8% and 88.1%, respectively. Fifty percent of recipients with high BAFF at day 7 (14 patients) and only 3.7% of patients with low BAFF demonstrated ABMR (P < 0.05). Indeed, ABMR was more common in patients high BAFF level (hazard ratio = 7.30; 95% CI = 3.77-14.15). The prevalence of ABMR among negative pre-transplant DSA/low BAFF, positive DSA/low BAFF, negative DSA/high BAFF, and positive DSA/ high BAFF recipients were 4.4, 0, 37.5 and 66.7%, respectively (P < 0.05).

CONCLUSIONS: Post-transplant ABMR can be predicted by perioperative serum BAFF level. Together with DSA testing, BAFF provides additional predictive value for ABMR.