Human Leukocyte Antigen-peptide complex (HLA-peptide complex)

Recipient HLA-peptide complexes are the primary immunological targets in allogeneic hematopoietic stem cell transplantation (HSCT) and related cellular immunotherapies. These complexes consist of a Human Leukocyte Antigen (HLA) molecule—either Class I or Class II—bound to a specific peptide fragment derived from host proteins, such as minor histocompatibility antigens (miHAs) or tumor-associated antigens [1, 2]. In the context of leukemia, donor-derived T cells recognize these complexes on the surface of malignant cells to mediate the Graft-versus-Leukemia (GvL) effect, which is the primary therapeutic mechanism for eradicating residual disease [3]. However, the recognition of these same complexes on healthy host tissues leads to Graft-versus-Host Disease (GvHD), a severe and potentially fatal systemic inflammatory condition [2]. Therapeutic strategies involve modulating the T-cell response to these complexes using immunosuppressants like tacrolimus or costimulation blockers like abatacept [4]. Emerging precision therapies, such as TCR-engineered T cells and TCR-mimetic antibodies, are designed to specifically target these complexes to maximize anti-tumor efficacy while minimizing off-target toxicity [3, 5].

Other names

MHC-peptide complexMinor histocompatibility antigen complexAlloantigenRecipient HLA-antigen complexmiHA-HLA complexpMHC

Recognition by donor T-cell receptors (TCRs) and subsequent activation of signaling pathways (e.g., calcineurin/NFAT) leading to T-cell proliferation and cytotoxic activity against cells presenting the complex.