LBP35: STRENGTH OF DE NOVO HLA DONOR SPECIFIC ANTIBODY IS A STRONG PREDICTOR OR ITS C1Q BINDING CAPABILITY

Abstract

Introduction Antibody mediated rejection (AMR) is the major complication of renal transplantation that significantly affects the renal allograft survival. Complement fixation mediated through Donor specific anti-Human Leukocyte Antigen (HLA) antibodies (DSA) is the hallmark of AMR. Different methods have been developed to detect DSA including Luminex single antigen beads (SAB) assay. However, it is still unclear how to define harmful DSA that causes poor graft outcomes. Aim We analyzed C1q assay positivity at different posttransplant time points and evaluated its relationship with different DSA characteristics including time of occurrence (early or late posttransplant), HLA class (class I, II or both) and Ab titre (mean fluorescence intensity, MFI). Method A total of 315 kidney transplant recipients between January 2007 and December 2012 were retrospectively analyzed for the presence of DSAs and their MFI using IgG SAB assay (One Lambda Inc., USA). Out of those, 39 patients with de novo DSA were further characterized using C1q assay. All 39 patients were followed for 2 years and their sera collected consequently with the protocol and/or diagnostic biopsies were analyzed by C1q assay (One Lambda Inc.). Results Most patients had at least 3 posttransplant sera during the 2-year follow up. The high MFI of HLA-IgG in all biopsy samples correlated significantly with C1q positivity. The mean MFI values of HLA-IgG for the negative and positive C1q were 2547 and 6424 ( p = 0.003), 2481 and 6130 ( p = 0.001) and 2200 and 8400 ( p = 0.009) for the sera collected at 6, 12 and 18-month posttransplant, respectively (Fig. 1). No other DSA characteristic correlated with C1q positivity. Conclusion The C1q assay is a potentially useful tool in allograft monitoring after transplantation. Our data indicates that Ab strength strongly correlates with the capacity to bind C1q. Correlation with clinical outcomes will further elaborate the relevance of C1q positivity on the renal allograft outcome.