HLA Antibody Identification with Single Antigen Beads Compared to Conventional Methods

Single antigen (SA) beads coated with Class I HLA antigens from recombinant cells lines were tested with 170 mouse monoclonal antibodies (mAbs). The HLA specificities of all mAbs were previously determined by the cytotoxicity assay (CDC). There were 100 mAbs which produced the expected reactions with the SA beads, indicating that the SA beads coated with the antigens had reacted properly. Sixty one mAbs were positive with one or more antigen(s) that shared unique amino acids (aa) possibly constituting a common epitope. Single antigen beads were then tested on 58 alloantisera analyzed by 63 laboratories of the UCLA serum exchange (UCLA-SE). Many specificities detected by the single antigen beads were missed by the laboratories employing conventional methods. Most of the missed specificities were of lower frequency, although in some instances, even common specificities were missed. These findings have important implications regarding the use of specificities to predict positive crossmatch, to selecting platelet donors for highly sensitized recipients, and analysis of sera for donor specific antibodies.