Endocytic recycling is required for the presentation of an exogenous peptide via MHC class II molecules

Sulabha S. Pathak, Janice S. Blum

Research output: Contribution to journalArticle

53 Scopus citations


Exogenous antigenic peptides captured and presented in the context of major histocompatibility (MHC) class II molecules on APC, have been employed as potent vaccine reagents capable of activating cellular immune responses. Binding and presentation of select peptide via surface class II molecules has been reported. Here, a role for endocytosis and early endosomes in the presentation of exogenous peptides via MHC class II molecules is described. T cell recognition of a 14 amino acid human serum albumin-derived peptide in the context of HLA-DR4 was observed only with metabolically active APC. The delayed kinetics and temperature dependence of functional peptide presentation via APC, were consistent with a requirement for peptide internalization to early endosomal compartments prior to T cell recognition. Ablating endocytosis by exposing cells to inhibitors of ATP production completely blocked the display of functional peptide:lass II complexes on the surface of the APC. Presentation of the peptide was also found to be sensitive to primaquine, a drug that perturbs the recycling of transport vesicles containing endocytic receptors and mature class II complexes. Functional presentation of the endocytosed peptide was dependent upon these mature class II complexes, as inhibitor studies ruled out a requirement for newly synthesized class II molecules. N-terminal processing of the endocytosed peptide was observed upon trafficking through endosomal compartments and linked to the formation of functional peptide:lass II complexes. These findings establish a novel mechanism for regulating class II-restricted peptide presentation via the endocytic pathway.

Original languageEnglish (US)
Pages (from-to)561-569
Number of pages9
Issue number7
StatePublished - 2000


  • Antigen presentation
  • Antigen processing
  • MHC class II
  • Recycling endosomes
  • Synthetic peptide

ASJC Scopus subject areas

  • Biochemistry
  • Cell Biology
  • Genetics
  • Molecular Biology
  • Structural Biology

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