Screening for antibodies against MICA by Luminex flow cytometry

Increased negative impact of donor HLA-specific together with non-HLA-specific antibodies on graft outcome

BACKGROUND

De novo donor HLA-specific (dnDSA) and non-HLA antibodies including antiangiotensin type 1 receptor antibodies (AT1R-abs) have been associated with antibody-mediated rejection (AMR) and decreased graft survival as well as cellular-mediated rejection (CMR) and early onset of microvasculopathy in heart transplantation. The aim of our study was to determine the impact of anti-AT1R-ab and anti-donor HLA-specific antibody (DSA) on clinical outcomes.

METHODS

Pretransplant and posttransplant sera from 200 recipients transplanted between May 2007 and August 2011 were tested for DSA (Luminex-based single antigen bead assay) and AT1R-ab (enzyme-linked immunosorbent assay). Two cutoff levels (≥ 17 and ≥ 12 units) were used to define high and intermediate binding of AT1R-ab. Clinical parameters examined were 5-year AMR/CMR (≥ grade 2), coronary artery vasculopathy, and survival.

RESULTS

At 2 years after transplant, freedom from AMR and/or CMR was 95.4% for those with no DSA (n=175), 66.9% for those with dnDSA (n=19), and 25% for those with DSA at transplant (n=6) (P<0.0001). Neither ≥ 17 nor ≥ 12 units of pretransplant levels indicated a significant difference in freedom from AMR and/or CMR. When both dnDSA and AT1R-ab ≥ 17 or ≥ 12 units were considered, freedom from AMR and/or CMR decreased to 50% and 45% (P<0.0001), respectively. Coronary artery vasculopathy and survival were not significantly impacted.

CONCLUSIONS

These results show the increased negative impact of dnDSA and AT1R-ab on freedom from AMR and/or CMR and an increased hazard ratio when both parameters are considered. Both HLA- and non-HLA-specific antibodies seem to impact graft outcome in heart transplantation.

Utility, reliability and reproducibility of immunoassay multiplex kits

Multiplex technologies are becoming increasingly important in biomarker studies as they enable patterns of biomolecules to be examined, which provide a more comprehensive depiction of disease than individual biomarkers. They are crucial in deciphering these patterns, but it is essential that they are endorsed for reliability, reproducibility and precision. Here we outline the theoretical basis of a variety of multiplex technologies: Bead-based multiplex immunoassays (i.e. Cytometric Bead Arrays, Luminex™ and Bio-Plex Pro™), microtitre plate-based arrays (i.e. Mesoscale Discovery (MSD) and Quantsys BioSciences QPlex), Slide-based Arrays (i.e. FastQuant™) and reverse phase protein arrays. Their utility, reliability and reproducibility are discussed.