Complement and Non-Complement Binding Anti-HLA Antibodies Are Differentially Detected with Different Antigen Bead Assays in Renal Transplant Recipients.

Two semi-quantitative, Luminex-based, single-antigen bead (SAB) assays are available to detect anti-HLA antibodies and evaluate their reactivity with complement binding. Sera from 97 patients with positive panel reactive antibody tests (>5%) were analyzed with two SAB tests, Immucor (IC) and One-Lambda (OL), for anti-HLA antibody detection and the evaluation of their complement-binding capacity. IC detected 1608/8148 (mean fluorescent intensity (MFI) 4195 (1995-11,272)) and 1136/7275 (MFI 6706 (2647-13,184)) positive anti-HLA class I and II specificities, respectively. Accordingly, OL detected 1942/8148 (MFI 6185 (2855-12,099)) and 1247/7275 (MFI 9498 (3630-17,702)) positive anti-HLA class I and II specificities, respectively. For the IC assay, 428/1608 (MFI 13,900 (9540-17,999)) and 409/1136 (MFI 11,832 (7128-16,531)) positive class I and II specificities bound C3d, respectively. Similarly, OL detected 485/1942 (MFI 15,452 (9369-23,095)) and 298/1247 (MFI18,852 (14,415-24,707)) C1q-binding class I and II specificities. OL was more sensitive in detecting class I and II anti-HLA antibodies than IC was, although there was no significant difference in the number of class II specificities per case. MFI was higher for complement vs. non-complement-binding anti-HLA antibodies in both assays. Both methods were equal in detecting complement-binding anti-HLA class I antibodies, whereas the C3d assay was more sensitive in detecting complement-binding anti-HLA class II antibodies.

Impact of de novo donor-specific HLA antibodies on pediatric kidney transplant prognosis in patients with acute declined or stable allograft function.

BACKGROUND: This retrospective multicenter long-term cohort study investigates de novo donor-specific HLA antibodies (dnDSA) impact on allograft survival in pediatric kidney transplantation (KTx), depending on allograft function at dnDSA detection. METHODS: Seventy patients with dnDSA screening in the context of acute allograft dysfunction (AAD) (>50% serum creatinine increase) or routine follow-up were included during a 20-year period. Number of dnDSA specificities and HLA total mean fluorescence intensity (MFI-sum) were collected. RESULTS: Median follow-up time was 8.6 years. Among the 22 dnDSA+ patients, 8 patients presented AAD. Compared with dnDSA- patients, allograft survival was shorter only in dnDSA+/AAD+ patients, regardless of dnDSA detection during the 5-year post-transplant period (9 patients) or later (13 patients) (log rank p < .001 and p < .001, respectively). One dnDSA+/AAD-, 7 dnDSA+/AAD+, and 5 dnDSA- patients lost their allograft. Allograft survival was shorter in dnDSA+/AAD+ patients compared with the 16 dnDSA-/AAD+ patients (log rank p < .001) but did not differ between dnDSA+/AAD- and dnDSA-/AAD- patients (log rank p = .157). dnDSA+/AAD+ and dnDSA-/AAD+ patients presented higher risk of allograft failure compared with the other patient groups after adjustment for recipient age at KTx, donor type, and incidence of delayed graft function (HR 11.322, 95% CI 3.094-41.429, p < .001). Concurrent MFI-sum >10 000 and multiple dnDSA specificities were more significantly associated with AAD, compared with each factor separately (p < .001). CONCLUSIONS: In pediatric KTx, AAD shortens allograft survival in dnDSA+ patients, regardless of dnDSA time detection, and is commonly observed when high MFI-sum concurs with multiple dnDSA specificities. dnDSA without AAD incidence does not determinately affect allograft survival.

Prospective De Novo Donor-Specific Antibody Monitoring in Renal Transplant Patients.

BACKGROUND: De novo donor-specific antibodies (dnDSA) are associated with antibody-mediated rejection leading to kidney transplant failure. However, many transplant patients are stable with no signs of graft dysfunction at the time of dnDSA detection at screening test. METHODS: We prospectively studied 26 kidney transplant patients for 3 years, with dnDSA detected using the Luminex single-antigen bead assay in a routine test. Proteinuria and estimated glomerular filtration rate were evaluated along with dnDSA monitoring at least annually. RESULTS: Graft loss associated with dnDSA occurred in 8 (31%) patients, 14 ± 11 months after the initial detection of dnDSA. These patients had more frequently multiple dnDSA (P = .004) and remarkable proteinuria, more than 1 g daily (P < .001). The remaining 18 patients were followed for 38 ± 15 months and considered stable as there was no deterioration regarding estimated glomerular filtration rate and proteinuria. In 7 (39%) of these patients, dnDSA waned and were not detected anymore at follow-up. Antibodies against HLA class I had a significantly (P < .001) lower mean fluorescence intensity (MFI) (2603 ± 1098) compared with those against HLA class II (11,109 ± 6414). In regression analysis, they were predictive of dnDSA wane (P = .043; odds ratio, 0.18; 95% confidence interval, 0.04-0.94). Despite fluctuations during follow-up, there was no significant change in MFI for those who retained the dnDSA. CONCLUSIONS: The presence of dnDSA is transient in a significant proportion of stable renal transplant patients, especially in those with antibodies against HLA class I and a low MFI. Multiple dnDSA and severe proteinuria adversely affect renal graft survival.