Virtual crossmatching and epitope analysis in kidney transplantation: What the physician involved in kidney transplantation should know?

Solid-phase single antigen bead (SAB) assay for detection of anti-human leukocyte antigen (HLA) antibodies and high-resolution HLA typing have enabled tremendous progress in virtual crossmatch (VXM) technology in recent years. However, misinterpretation of the SAB assay may result in detrimental consequences after kidney transplantation. Meanwhile, epitope analysis could be an effective method to estimate immunizing eplets, which may provide ancillary information for better understanding of the SAB assay. To perform epitope analysis appropriately, it is necessary to understand the basic principles related to histocompatibility testing and the characteristics of the SAB assay. Therefore, knowledge of the properties and limitations of the SAB assay is critical. In this review, we aim to describe the fundamental concepts regarding immunobiological assessment, including HLA, anti-HLA antibodies, and SAB assay, and explain epitope analysis using examples.