Elevated serum levels of B-cell activating factor in pediatric renal transplant patients

Investigating the Role of BAFF and Its Receptors in Renal Transplant Recipients with Chronic Antibody-Mediated Rejection

Background

Kidney transplantation is the best treatment option for end stage renal disease (ESRD), but graft rejection is still a big obstacle that occurs in spite of immunosuppressive therapy. B cells are considered as the major reason for renal graft rejection because of antibody production. Due to their roles in B cell function, we intended to evaluate the B cell activating factor (BAFF) and its receptors including BAFF receptor (BAFF-R), B cell maturation antigen (BCMA), and transmembrane activator and cyclophilin ligand interactor (TACI) in renal transplant patients.

Method

The study included 40 kidney allograft patients with cAMR, 40 stable kidney allograft patients, and 8 healthy volunteers with normal kidney function. The percentage and absolute number of CD19⁺ B cells were analyzed by flow cytometry, the serum level of BAFF was analyzed by ELISA, and mRNA expressions of BAFF and BAFF receptors (BAFF-R, BCMA, and TACI) were measured using quantitative real-time PCR.

Results

The percentage and the absolute number of B cells decreased significantly in stable and cAMR patients compared to healthy individuals. The serum level and gene expression of BAFF, as well as the mRNA level of BCMA, were increased significantly in both cAMR and stable patients compared to healthy volunteers. There was an overexpression of TACI mRNA in cAMR patients compared to stable patients.

Conclusions

Both soluble protein and mRNA transcript of BAFF increased in transplant recipients. However, BAFF neither at the serum level nor at the mRNA transcript level cannot be a good biomarker for the prediction of cAMR. In addition, expression of TACI, compared to other receptors of BAFF, confers a potential to be used in distinguishing cAMR and stable kidney transplant patients.

The role of soluble B cell-activating factor in further stratifying the risk of antibody-mediated rejection post-renal transplant: A meta-analysis

BACKGROUND

We conducted a meta-analysis to evaluate the predictive value of serum soluble B cell-activating factor (sBAFF) for antibody-mediated rejection (ABMR), which remains controversial.

METHODS

Systematic literature search was performed in PubMed, EMBASE, Scopus, Cochrane Library, Web of Science and three Chinese databases. Studies of any relevant design were included. Random and fixed-effects meta-analytical models were used. Study quality, publication bias, and heterogeneity were assessed. This study was registered with PROSPERO (CRD42019109198).

RESULTS

Nine observational studies were included in the meta-analysis, including 1302 cases (median NOS quality score = 8, range 6-8). The incidence of ABMR was significantly higher in the high sBAFF group than in the low sBAFF level group (Risk ratio [RR] 2.04 [95% CI 1.52-2.74], I² = 26%, P < 0.01, N = 1014). The subgroup analysis showed that regardless of pre-transplant donor-specific antibody (DSA) status, the high sBAFF level group still had a significantly higher incidence of ABMR. sBAFF was not associated with the risk of TCMR. The sBAFF level was significantly higher in the anti-HLA-antibody (+) group than in anti-HLA-antibody (-) patients before or after kidney transplantation (Standardized mean difference [SMD] 0.43 [0.29-0.56], P < 0.01, I² = 34%, N = 1001).

CONCLUSION

sBAFF is a promising biomarker to further stratify the risk of ABMR post-renal transplant.

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.

B Cell Activating Factor, Renal Allograft Antibody-Mediated Rejection, and Long-Term Outcome

Antibody-mediated rejection (ABMR) of renal allograft lacks typical phenotypes and clinical manifestations, always resulting in delayed diagnosis and treatment. It has been considered to be an elemental factor influencing the improvement of the long-term outcome of renal allograft. The B cell activating factor (BAFF) signal plays a fundamental function in the process of antibody-mediated immune response. Data from recipients and the nonhuman primate ABMR model suggest that the BAFF signal participates in the ABMR of renal allograft, while there are objections. The challenges in the diagnosis of ABMR, different study population, and details of research may explain the discrepancy. Large quantities of dynamic, credible data of BAFF ligands and their association with renal allograft pathological characteristics would constitute a direct proof of the role of BAFF in the progression of renal allograft ABMR.

Serum miR-338-5p, soluble B-cell-activating factor, allo-antibodies, and renal transplantation

BACKGROUND

The objective of the study was to explore the expression features of serum miR-338-5p and soluble B-cell-activating factor (sBAFF) in renal transplant recipients.

METHODS

Follow-up renal transplant recipients (n = 49) were enrolled in this study (male/female: 38/11). Healthy volunteers were controlled; 2 mL of peripheral blood from each subject was collected. Total RNA was extracted from serum by use of the miRNeasy Serum/Plasma Kit (QIAGEN), and miR-338-5p was amplified by means of quantitative real-time reverse transcriptase-polymerase chain reaction. sBAFF was detected by means of enzyme-linked immunoassay. LABScreen Mix (LSM12) (One Lambda) was used to test the level of anti-human leukocyte antigen (HLA) I antibody (Ab), anti-HLA II Ab, and anti-major histocompatibility complex class I chain-related A (MICA) Ab. All data are shown as mean ± SD and were analyzed by use of SPSS software 17.0.

RESULTS

Compared with healthy volunteers, serum miR-338-5p in recipients was statistically downregulated (2.79 ± 2.5 versus 0.09 ± 0.12, P < .001); sBAFF in recipients was significantly upregulated (1321 ± 950 pg/mL versus 534 ± 327 pg/mL, P < .01); serum anti-HLAII Ab, anti-MICA Ab, and anti-HLA+MICA Abs all statistically increased in recipients (P < .05). Spearman correlation analysis showed that miR-338-5p was significantly negatively correlated with sBAFF (r = -0.51, P < .001) and anti-HLA II antibody with mean fluorescence intensity value >1000 (r = -0.322, P < .05). Analysis results also suggested that sBAFF was significantly negatively correlated with anti-MICA Ab, with mean fluorescence intensity value >1000 (r = -0.579, P < .05).

CONCLUSIONS

miR-338-5p is closely correlated with the procedure of renal allograft antibody-mediated rejection.

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.

Longitudinal analysis of T and B cell phenotype and function in renal transplant recipients with or without rituximab induction therapy

Background

Prevention of rejection after renal transplantation requires treatment with immunosuppressive drugs. Data on their in vivo effects on T- and B-cell phenotype and function are limited.

Methods

In a randomized double-blind placebo-controlled study to prevent renal allograft rejection, patients were treated with tacrolimus, mycophenolate mofetil (MMF), steroids, and a single dose of rituximab or placebo during transplant surgery. In a subset of patients, we analyzed the number and phenotype of peripheral T and B cells by multiparameter flow cytometry before transplantation, and at 3, 6, 12, and 24 months after transplantation.

Results

In patients treated with tacrolimus/MMF/steroids the proportion of central memory CD4⁺ and CD8⁺ T cells was higher at 3 months post-transplant compared to pre-transplant levels. In addition, the ratio between the percentage of central memory CD4⁺ and CD4⁺ regulatory T cells was significantly higher up to 24 months post-transplant compared to pre-transplant levels. Interestingly, treatment with tacrolimus/MMF/steroids resulted in a shift toward a more memory-like B-cell phenotype post-transplant. Addition of a single dose of rituximab resulted in a long-lasting B-cell depletion. At 12 months post-transplant, the small fraction of repopulated B cells consisted of a high percentage of transitional B cells. Rituximab treatment had no effect on the T-cell phenotype and function post-transplant.

Conclusions

Renal transplant recipients treated with tacrolimus/MMF/steroids show an altered memory T and B-cell compartment post-transplant. Additional B-cell depletion by rituximab leads to a relative increase of transitional and memory-like B cells, without affecting T-cell phenotype and function.

Trial Registration

ClinicalTrials.gov NCT00565331

Four-year allograft survival in a highly sensitized combined liver-kidney transplant patient despite unsuccessful anti-HLA antibody reduction with rituximab, splenectomy, and bortezomib

Although donor-specific lymphocytotoxic antibodies are regarded as a contraindication for kidney transplantation (KTx), the data available for liver or combined liver or kidney transplantation (cLKTx) are scarce. Here, we report a case of a highly sensitized young man receiving his sixth liver and second kidney graft. Multiple anti-HLA antibodies were present at the time of transplantation. As a result of suspected antibody-mediated graft damage, the patient was treated with rituximab, plasmapheresis, intravenous immunoglobulins, splenectomy, and bortezomib to decrease the antibody production. So far, patient and allograft survival has reached 4 years despite failure to achieve a permanent reduction of anti-HLA antibodies, and particularly nondonor directed antibodies.