Host Peptide-Major Histocompatibility Complex (Host pMHC)

Host peptide-Major Histocompatibility Complex (pMHC) complexes on recipient cells are the central ligands in the direct pathway of allorecognition, where donor T cells directly recognize intact host MHC molecules [1][2]. These complexes are composed of a host-derived peptide—often a minor histocompatibility antigen—bound to a host MHC molecule (HLA in humans) expressed on the surface of recipient tissues or antigen-presenting cells [2][3]. This recognition is the initiating event in acute Graft-versus-Host Disease (GvHD), where donor T cells perceive the host pMHC as foreign, leading to a robust inflammatory response and tissue destruction [1][4]. Current therapeutic strategies do not typically target the pMHC directly but instead focus on inhibiting the resulting T-cell activation using calcineurin inhibitors or costimulation blockers [4][5]. Managing the interaction with host pMHC is a delicate balance in transplantation, as complete suppression can eliminate the beneficial graft-versus-leukemia effect and leave the patient vulnerable to life-threatening infections [2][5].

Other names

Recipient pMHCHost HLA-peptide complexAllogeneic MHC-peptide complexMinor histocompatibility antigen-MHC complexDirect allorecognition target

Inhibition of T-cell activation following pMHC recognition, blockade of costimulatory signals (e.g., CD80/86-CD28), or depletion of alloreactive T cells.