Transplantation is a life saving procedure for patients with end stage diseases, traumatic injuries, blood diseases or metabolic disorders. For solid organs or tissues the most common type of transplantation performed is allogenic grafts that contain genetic mismatches between the human leukocyte antigen (HLA; human major histocompatibility complex [MHC]) molecules carried by the donor and recipient. HLA mismatches can trigger destructive immune responses leading to graft rejection and loss. Recipient T cells that mediate these immune responses recognise foreign donor HLA molecules in complex with self-peptides (1). A major limitation following transplantation has been an inability to identify the peptide/HLA targets involved in graft rejection and the alloreactive T cells that directly recognise them. We recently reported in mice that the donor immunopeptidome (array of peptides presented by MHC molecules) provides strong immunogenic targets for recipient alloreactive T cells that mediate anti-graft responses. Importantly, we have shown that as few as 5 different peptide antigens commonly expressed by three different tissues (i.e. hepatocytes, spleen, skin) trigger ~40% of alloreactive T cells, demonstrating that there are immunodominant allogeneic peptide/MHC complexes that account for a large proportion of the anti-graft response (2). In this study, we explored the human immunopeptidome of transplantable organs (i.e. heart, lung, kidney, liver) from 5 HLA-A*02:01-positive donors to profile both commonly expressed and tissue-specific peptides presented by a globally highly prevalent HLA allotype. Briefly, 100-300 mg of tissue was used for the immunoaffinity purification of peptide/HLA class I and class II complexes and the peptides isolated for analysis by LC-MS/MS on a Bruker timsTOF Pro2. Data were searched with PEAKS Xpro studio software against the Homo sapiens UniProt database. Matched tissue-specific proteomics data is also available from each sample. We anticipate that the ATLANTIS database will allow for the identification of donor-derived peptide antigens that drive anti-graft immune responses, which will be critical for future development of diagnostic reagents for post-transplant immune monitoring.