The human leukocyte antigen-presented ligandome of B lymphocytes

Peptides presented by human leukocyte antigen (HLA) molecules on the cell surface play a crucial role in adaptive immunology, mediating the communication between T cells and antigen presenting cells. Knowledge of these peptides is of pivotal importance in fundamental studies on T cell action, and in cellular immunotherapy and transplantation. In this study we present the in-depth identification and relative quantification of 14,500 peptide ligands constituting the HLA-ligandome of B-cells. This large number of identified ligands provides a general insight in the presented peptide repertoire and antigen presentation. Our uniquely large set of HLA-ligands allowed us to characterize in detail the peptides constituting the ligandome in terms of relative abundance, peptide length distribution, physicochemical properties, binding affinity to the HLA molecule and presence of post-translational modifications. The presented B-lymphocyte ligandome is shown to be a rich source of information by the presence of minor histocompatibility antigens, virus-derived epitopes and post-translationally modified HLA ligands and can be a good starting point to solve a wealth of specific immunological questions. These HLA ligands can form the basis for reversed immunology approaches to identify T cell epitopes, not based on in silico predictions, but based on the bona fide eluted HLA-ligandome