Allogeneic Human Leukocyte Antigen and Minor Histocompatibility Antigen Complexes (HLA/mHAg complexes)

Allogeneic Human Leukocyte Antigen (HLA) and minor histocompatibility antigen (mHAg) complexes are the primary molecular targets recognized by the immune system during allogeneic hematopoietic stem cell transplantation (HSCT) and organ transplantation (NIH, 2023). HLA molecules are highly polymorphic cell surface glycoproteins that present peptide fragments to T cells to facilitate immune surveillance and self-nonself discrimination (UniProt, 2024). When these complexes on recipient cells are recognized as foreign by donor-derived T cells, they trigger a potent immune response known as Graft-versus-Host Disease (GvHD), which can lead to severe tissue damage in the skin, liver, and gastrointestinal tract (StatPearls, 2023). Minor histocompatibility antigens are peptides derived from polymorphic proteins that differ between donor and recipient, even in HLA-matched pairs, further contributing to immune activation and transplant complications (PubMed, 2022). Therapeutic strategies often focus on suppressing the T-cell signaling pathways initiated by this recognition or depleting the reactive T-cell populations using drugs like tacrolimus, cyclosporine, or abatacept (Mayo Clinic, 2024). Understanding these complexes is crucial for improving transplant outcomes and developing targeted therapies, such as TCR-like antibodies or engineered T-cells, that can induce tolerance without broad immunosuppression.

Other names

Allo-HLAMinor histocompatibility antigensmHAgMHC-peptide complexesHistocompatibility antigensRecipient alloantigens

Inhibition of T-cell activation, proliferation, or costimulation triggered by the recognition of non-self HLA or minor histocompatibility antigens on host tissues.