BLEAT leader assignment. Two scenarios are depicted using the 2 HLA-B alleles from 1 subject to illustrate a simple use case (HLA-B*07:06:01) and a more complex use case (HLA-B*56:01:01G). For clarity, only the last 5 alleles (by number) are displayed for HLA-B*56:01:01G.³⁶  (A) The leader peptide is deduced from the exon 1 sequence. (B) The deduced leader peptide is available from IMGT in the Anthony Nolan HLA Informatics Group GitHub repository.³⁵  (C) This information is processed and reflected on BLEAT’s user interface to display P2 information. The user may hover over the P2 “Leader” icon to reveal a tooltip (D) that organizes all potential HLA-B alleles from the provided allele into known and unknown major (and any minor, if applicable) leader alleles. Rare minor leader alleles are highlighted with red on the user interface.