A Short History of B-Cell HLA Epitopes

Background: HLA epitopes are currently in the focus of transplantation immunogenetics. The main reason is the complexity of the HLA system with >38,000 alleles, the number of which increases steadily. These alleles are determined by the current state-of-the art typing methods like second- and third-generation sequencing. Screening for HLA antibodies is hampered by the lack of specific target beads with all possible alleles described. Summary: A way to circumvent the problem is to define HLA epitopes. The number of antibody-confirmed epitopes, on the other hand, was found to be 72 for HLA class I and 74 for HLA class II. Here, we elaborate on the current knowledge on these HLA epitopes. Absolute definitions of these structures are not yet available. Key Messages: Making use of eplets is a comparable way allowing statistical analyses. However, one should keep in mind that the results obtained are approximative or perhaps better associative. Continuous collaboration is needed for the full understanding of the HLA epitopes. The reactivity toward epitopes remains patient-specific.