Host alloantigen or self-peptide–Human Leukocyte Antigen complex (pHLA)

The host alloantigen or self-peptide–Human Leukocyte Antigen (HLA) complex is a fundamental molecular structure on the surface of host cells that presents internal protein fragments to T cells. These complexes are composed of a peptide derived from the cell's own proteome (self-peptide) or from a donor's proteome in the case of transplantation (alloantigen), bound to the polymorphic groove of an HLA molecule (Janeway's Immunobiology, 9th Ed). Their primary biological role is to facilitate immune surveillance and maintain self-tolerance by acting as the specific ligand for T-cell receptors (TCRs) (PMID: 30559448). In the context of disease, these complexes are the primary drivers of transplant rejection and graft-versus-host disease (GVHD), where the recipient's or donor's T cells recognize foreign HLA-peptide combinations (Abbas et al., Cellular and Molecular Immunology). Furthermore, in autoimmune diseases, the immune system inappropriately targets self-peptide-HLA complexes, leading to tissue destruction (PMID: 29427171). Therapeutic strategies targeting these interactions include immunosuppressive drugs like Abatacept, which modulates T-cell costimulation, and emerging TCR-engineered T-cell therapies that specifically target pHLA complexes overexpressed in certain conditions (FDA, Afamitresgene autoleucel). Understanding the specificity of these complexes is crucial for developing precision immunotherapies that avoid off-target cross-reactivity with essential self-antigens (PMID: 27135737).

Other names

Self-peptide-MHC complexpMHCAllo-HLAMajor histocompatibility complex-peptide complexAlloantigen-HLA complexSelf-pMHC

Modulation of T-cell receptor (TCR) binding or downstream signaling to either inhibit or activate immune responses against specific peptide-HLA presentations.