peptideHLA

PeptideHLA refers to the peptide-HLA complex, formed when a peptide binds to a human leukocyte antigen (HLA) molecule on the surface of a cell. These complexes are presented to T cells by MHC class I and class II molecules and are central to the recognition of self versus non-self and of infected or transformed cells.

In MHC class I, intracellular proteins are degraded by the proteasome, peptides are transported into the endoplasmic reticulum by TAP, and loaded onto HLA-A, -B, or -C molecules with chaperones guiding folding; the complex then travels to the cell surface.

In MHC class II, extracellular proteins are taken up into endosomes, cleaved into peptides, the invariant chain blocks the groove, CLIP is exchanged by HLA-DM, and peptide-HLA II complexes are presented to CD4+ T cells.

Binding characteristics: the groove of each HLA allele has motif preferences; Class I peptides are typically 8-11 amino acids in length, while Class II peptides are longer (13-25 aa) with flexible ends. Binding affinity and stability influence T cell activation and the quality of the immune response.

PeptideHLA complexes underpin immune surveillance, transplant compatibility, and the design of vaccines and cancer immunotherapies. They are studied by mass spectrometry and tetramer staining, and are predicted computationally to identify potential neoantigens for therapeutic applications.