35-P

Abstract

Aim Exposure to non-self HLA epitopes can result in the production of HLA antibodies to eiptopes that are shared between different antigens and make the interpretation of single antigen beads (SAB) assay complex. This case report shows a sensitized kidney transplant candidate with weak HLA antibodies against all but except self HLA-A locus antibodies. Methods Lumines SAB analysis were performed using the LABScreen®. Epitope analysis was performed using ClustalW2 multiple sequence alignment program for proteins (EMBL-EBI). Flow cytometry crossmatch with the standard B cell lines obtained from the IHWG as well as cells from HLA typed healthy volunteers. Results Luminex Single Antigen beads showed very low levels of antibodies to all A locus antigens but A30 (Fig. 1). The majority of these antibodies would not be called if MFI cut-off was used as the only metric. Sequence alignment analysis indicated the presence of shared non-self A locus epitope. Crossmatch with standard B cells and normal healthy donors were all positive except donors that are A30 (self). Further flow up on this patient showed an elevation of the same antibodies (Fig. 2). Conclusions The use of the signal strength expressed in MFI as the only determinant for the single antigen beads data analysis may not be always correct in cases with antibodies directed to non-well characterized shared epitopes. (Figs. 1 and 2)