External glycopeptide binding to MHC class-I in relation to expression of TAP transporters, β2-microglobulin and to pH

• Published in: Immunology letters 1996-12, Vol.54 (1), p.31-35
• Main Authors: Abdel-Motal, Ussama M., Dahmén, Jan, Liu, Tianmin, Ljunggren, Hans-Gustaf, Jondal, Mikael
• Format: Article
• Language: English
• Subjects: Endosomes; MHC class-I; Peptide; Transporter associated with antigen processing
• ISSN: 0165-2478; 1879-0542
• DOI: 10.1016/S0165-2478(96)02637-5

MHC class-I binding glycopeptides are easily visualized on the cell surface by carbohydrate specific monoclonal antibodies. By comparing the staining intensity between anti-carbohydrate and anti-MHC class-I specific monoclonal antibodies, an estimation of the fraction of peptide accessible ‘empty’ sites on the cell surface of MHC class-I molecules can be made. This system was used to analyze glycopeptide binding to MHC class-I molecules in relation to transporter associated with antigen processing (TAP) peptide transporters and β2-M expression, using gene targeted mice, and in relation to pH. Approximately 15, 40, and 95% ‘empty’ D b molecules were found on activated T cells from normal, β2-M-/- and TAP -/- mice, respectively. The ASN9-6h-Gal 2 glycopeptide also bound to transfected ‘empty’ D b molecules on T1-D b, T2-D b and T3-D b cells with a preference for T2-D b cells, lacking TAP peptide transporters. The stability of glycopeptide binding to H-2D b is also highest on T2-D b cells. pH was found to influence binding either positively or negatively, using four different glycopeptides, binding either to D b or K b. We conclude that external glycopeptide binding may reflect important functional properties in the MHC class-I system and that pH in different processing compartments might influence the expressed peptide repertoire.