antigen presentation

MHC Class I vs II Peptide Binding: T Cell Presentation Explained

Adaptive immunity relies on T cell recognition of peptide-MHC complexes. MHC class I binds short endogenous peptides (8-10 amino acids) in a closed groove, presenting to CD8+ cytotoxic T cells. MHC class II binds longer exogenous peptides (13-25 amino acids) in an open groove, presenting to CD4+ helper T cells. Understanding these structural and functional differences is key for designing peptide-based vaccines and T cell assays.