Utility of HLA Antibody Testing in Kidney Transplantation

Abstract

HLA antigens are polymorphic proteins expressed on donor kidney allograft endothelium and are critical targets for recipient immune recognition. HLA antibodies are risk factors for acute and chronic rejection and allograft loss. Solid-phase immunoassays for HLA antibody detection represent a major advance in sensitivity and specificity over cell-based methods and are widely used in organ allocation and pretransplant risk assessment. Post-transplant, development of de novo donorspecific HLA antibodies and/or increase in donor-specific antibodies from pretransplant levels are associated with adverse outcomes. Although single antigen bead assays have allowed sensitive detection of recipient HLA antibodies and their specificities, a number of interpretive considerations must be appreciated to understand test results in clinical and research contexts. This review, which is especially relevant for clinicians caring for transplant patients, discusses the technical aspects of single antigen bead assays, emphasizes their quantitative limitations, and explores the utility of HLA antibody testing in identifying and managing important pre-and post-transplant clinical outcomes.

Interpreting Anti-HLA Antibody Testing Data

“…Laboratory variability exists because of differences in the SAB product itself depending on the bead manufacturer, batch, or lot (19-21). Manufacturers have different antigen sources, distinctive specificity representation, and varied antigen density on the beads [18].…”

“…Manufacturers have different antigen sources, distinctive specificity representation, and varied antigen density on the beads [18]. Even with identical product; intra-laboratory variability can occur depending on laboratory personnel, reagents, equipment, and conditions (19, 20, 22). As with any test using flow fluorescent technology there is also background fluorescence.…”

“…Alloantibody can bind a shared epitope on multiple antigens resulting in the positivity of more than 1 bead (19, 32-34). The strength of this antibody would be diluted and underrepresent its clinical importance if the donor cell only has 1 of these antigens.…”

Monitoring alloimmune response in kidney transplantation

“…Even though the issue of hyperacute allograft rejection has been almost overcome by the introduction of novel crossmatch techniques [74], and more sensitive assays measuring the presence of circulating anti-HLA antibodies both before and also after transplantation [75], the persistence of humoral immunity against donor antigens still remains as the main cause leading to allograft rejection in the mid/long term.…”

The functional role of B cells and their secreted antibodies

“…Although the CDC assays are costeffective and correlated significantly with graft outcome, these assays also showed a limited sensitivity and specificity. The SPA platforms can range from ELISAs to the more sensitive flow cytometry-based microspheres such as multiplex-bead arrays using Luminex technology 383,384 . There are three types of resolution in SPA assays: (1) …”