Long-term follow up for anti-HLA donor specific antibodies postrenal transplantation: high immunogenicity of HLA class II graft molecules.

Τhe clinical significance of de novo post-transplant anti-HLA donor-specific antibodies (DSA) was evaluated using 4241 serum samples collected between 2000 and 2007 from 597 renal transplant recipients. Patients transplanted before December 1996 (n = 77) were included in the historic group and those transplanted thereafter (n = 520) were included in the study group. All recipients were negative for DSA before transplantation (Tx). Post-Tx, de novo DSA were detected in 92/597 (15.4%) patients, while 196 had third party anti-HLA antibodies (DSA-negative). DSA were more frequent in the historic group (33.8%) compared with the study group (12.7%) (P < 0.001). Anti-HLA class-II DSA predominated in both groups (84.6% vs. 69.7%). Recipients of HLA class II-incompatible grafts developed DSA more frequently than those receiving HLA class II-compatible grafts (17.9% vs.7.9%, P = 0.003), directed mainly against HLA-DQ graft molecules (64/446, 14.4%). DSA production was not different between presensitized and nonsensitized patients (P = 0.842). Graft survival was higher in patients without antibodies compared with DSA-positive (log-rank test, P = 0.002) and DSA-negative patients (log-rank test, P = 0.002). Univariate and multivariate analysis showed independent association for DSA class I (HR = 31.78), DSA class II (HR = 20.92) and non-DSA (HR = 5.94) and graft failure. We conclude that HLA class II incompatible graft transplantations need careful monitoring and should be avoided in high immunological risk cases.