Peptide–major histocompatibility complex on antigen-presenting cell (Peptide–MHC complex (on APC))

The **peptide–major histocompatibility complex (MHC) complex on antigen-presenting cells** is a molecular structure formed when a peptide (typically a short fragment derived from pathogens, abnormal proteins, or self-antigens) is bound and presented by an MHC molecule on the surface of an antigen-presenting cell (APC), such as a dendritic cell, macrophage, or B lymphocyte[1][3][5]. There are two main classes relevant for antigen presentation: MHC class I molecules, which present endogenous (intracellular) peptides to CD8+ cytotoxic T cells, and MHC class II molecules, which present exogenous (extracellular) peptides to CD4+ helper T cells[1][2]. The peptide–MHC complex (pMHC) is essential for immune surveillance, allowing T cells to recognize and respond to infected, transformed, or foreign cells[2][3]. The MHC genes are highly polymorphic, resulting in significant diversity in antigen presentation and immune response among individuals[3][5]. Disruption or dysregulation of pMHC recognition is implicated in immunological diseases, including infection, cancer, autoimmunity, and transplant rejection[3][5][4]. **Note:** The "peptide–MHC complex on antigen-presenting cells" is a molecular entity and central immune ligand, not a classical single-molecule "receptor," but it is a critical target for therapeutic agents that modulate T cell responses, vaccines, and diagnostics[1][4][5].

Other names

Peptide–MHC complexpMHC complexPeptide-bound MHC moleculePeptide–major histocompatibility complexAntigen–MHC complex

- Modulation of T cell activation by altering pMHC-TCR interaction - Immune checkpoint blockade (by interfering with downstream signaling after pMHC recognition) - Induction of immune tolerance/desensitization (altering antigenicity of pMHC) - Targeted cell lysis (via redirected TCR or CAR-T therapy recognizing specific pMHC)