NEW CHOICES FOR PATIENTS NEEDING KIDNEY TRANSPLANTATION ACROSS ANTIBODY BARRIERS

Subclass analysis of donor HLA-specific IgG in antibody-incompatible renal transplantation reveals a significant association of IgG4 with rejection and graft failure

Donor HLA‐specific antibodies (DSAs) can cause rejection and graft loss after renal transplantation, but their levels measured by the current assays are not fully predictive of outcomes. We investigated whether IgG subclasses of DSA were associated with early rejection and graft failure. DSA levels were determined pretreatment, at the day of peak pan‐IgG level and at 30 days post‐transplantation in eighty HLA antibody‐incompatible kidney transplant recipients using a modified microbead assay. Pretreatment IgG₄ levels were predictive of acute antibody‐mediated rejection (P = 0.003) in the first 30 days post‐transplant. Pre‐treatment presence of IgG₄DSA (P = 0.008) and day 30 IgG₃DSA (P = 0.03) was associated with poor graft survival. Multivariate regression analysis showed that in addition to pan‐IgG levels, total IgG₄ levels were an independent risk factor for early rejection when measured pretreatment, and the presence of pretreatment IgG₄DSA was also an independent risk factor for graft failure. Pretreatment IgG₄DSA levels correlated independently with higher risk of early rejection episodes and medium‐term death‐censored graft survival. Thus, pretreatment IgG₄DSA may be used as a biomarker to predict and risk stratify cases with higher levels of pan‐IgG DSA in HLA antibody‐incompatible transplantation. Further investigations are needed to confirm our results.

The HLA system: immunobiology, HLA typing, antibody screening and crossmatching techniques

The Human Leukocyte Antigen (HLA) system plays a critical role in regulating the immune response. As a consequence of its role in immune regulation and exquisite polymorphism, the HLA system also constitutes an immunological barrier which must be avoided or otherwise overcome in clinical transplantation. This introductory review provides a brief summary of the immunobiology of the HLA system and methodology for HLA typing, antibody screening and patient-donor cross-matching. This constitutes a basis for consideration of the importance of these procedures in the system-specific reviews which follow.