Peptide-receptive class I major histocompatibility complex molecules on TAP-deficient and wild-type cells and their roles in the processing of exogenous antigens

Immunology. 1999 Jun;97(2):316-24. doi: 10.1046/j.1365-2567.1999.00759.x.


These studies addressed the nature and origin of peptide-receptive class I major histocompatibility complex (MHC-I) molecules used to present exogenous antigens. Peptide-receptive Kb molecules in transporter for antigen presentation (TAP)1-/- and TAP1+/+ macrophages were quantitated by exposing cells to exogenous ovalbumin (OVA)(257-264) peptide and then measuring OVA(257-264):Kb complexes with a T hybridoma assay or flow cytometry (using a complex-specific antibody). Relative to TAP1+/+ cells, TAP1-/- cells had decreased levels of pre-existing cell-surface peptide-receptive MHC-I molecules at 37 degrees. With continued exposure of viable cells to peptide, however, TAP1-/- and TAP1+/+ cells formed similar levels of OVA(257-264):Kb complexes, suggesting that nascent labile MHC-I molecules were captured and stabilized by exogenous peptide. Brefeldin A inhibited generation of OVA(257-264):Kb complexes on TAP1-/- (but not TAP1+/+) cells at 37 degrees, confirming the importance of a flux of unstable nascent MHC-I molecules in TAP1-/- cells at 37 degrees. In contrast, at 26 degrees both TAP1-/- and TAP1+/+ cells expressed brefeldin A-resistant, peptide-receptive MHC-I molecules at similar levels. Alternate MHC-I processing of exogenous particulate antigen correlated with ability to present exogenous peptide. Thus, processing was brefeldin A-sensitive with TAP1-/- macrophages at 37 degrees, but brefeldin A-resistant with TAP1+/+ cells at 37 degrees, as well as with TAP1+/+ or TAP1-/- cells at 26 degrees. We conclude that alternate MHC-I antigen processing normally utilizes pre-existing MHC-I molecules, but TAP1-/- cells at 37 degrees mainly use nascent MHC-I molecules, because of a lack of pre-existing, stable, peptide-receptive MHC-I molecules. The results support a vacuolar processing mechanism with binding of peptides to MHC-I molecules in post-Golgi compartments or on the cell surface.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • ATP Binding Cassette Transporter, Subfamily B, Member 2
  • ATP-Binding Cassette Transporters / immunology*
  • Animals
  • Antigen Presentation / drug effects
  • Antigen Presentation / immunology*
  • Brefeldin A / pharmacology
  • Cell Culture Techniques
  • Histocompatibility Antigens Class I / immunology*
  • Macrophages, Peritoneal / immunology
  • Mice
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Ovalbumin / immunology
  • Peptide Fragments / immunology*
  • Protein Synthesis Inhibitors / pharmacology
  • Temperature


  • ATP Binding Cassette Transporter, Subfamily B, Member 2
  • ATP-Binding Cassette Transporters
  • Histocompatibility Antigens Class I
  • Peptide Fragments
  • Protein Synthesis Inhibitors
  • TAP1 protein, human
  • Tap1 protein, mouse
  • Brefeldin A
  • Ovalbumin