Chronic graft versus host disease is associated with an immune response to autologous human leukocyte antigen-derived peptides

Background. Chronic graft-versus-host disease (cGVHD) is a major complication of allogeneic bone marrow transplantation (BMT) the immunopathogenesis of which is not well understood. Humoral and cellular immunity are both implicated, patients express a range of autoantibodies, but the targets of cellular immunity are not well defined. Autologous human leukocyte antigen (HLA)-derived peptides constitute a significant proportion of the repertoire. Methods. We have investigated the response to HLA-derived peptides after allogeneic BMT using γ-interferon enzyme-linked immunospot assay (ELISPOT). We also studied the release of this γ-interferon by flow cytometry in a subgroup of responsive patients. Results. The peripheral blood mononuclear cell response was assessed by γ-interferon ELISPOT in 42 BMT recipients (21 with cGVHD) and 30 healthy donors. Thirteen of 21 patients diagnosed with cGVHD responded to at least one HLA-derived peptide compared with 1 of 21 patients without cGVHD (62% vs. 5%, P<10^-4) and 1 of 30 healthy donors. In all but one patient these peptides correspond with the sequences of autologous HLA. The median single peptide-specific response in ELISPOT was 43/10⁶ peripheral blood mononuclear cells. In a subgroup studied by flow cytometry, γ-interferon production to individual peptides occurred in 0.04% to 0.18% of CD4⁺ T lymphocytes. Conclusion. These observations identify HLA-derived peptides as targets of a cellular immune response in cGVHD.