Effects of pH and Polysaccharides on Peptide Binding to Class II Major Histocompatibility Complex Molecules

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 88; no. 7; pp. 2740 - 2744
• Main Authors: Harding, Clifford V., Roof, Richard W., Allen, Paul M., Unanue, Emil R.
• Format: Journal Article
• Language: English
• Published: Washington, DC National Academy of Sciences of the United States of America 01.04.1991; National Acad Sciences
• Subjects: 550201 - Biochemistry- Tracer Techniques; ANIMAL CELLS; Animals; Antigen presentation; Antigen-Presenting Cells - immunology; ANTIGENS; BASIC BIOLOGICAL SCIENCES; BETA DECAY RADIOISOTOPES; Biological and medical sciences; BIOLOGICAL EFFECTS; BIOLOGICAL MATERIALS; BLOOD; BLOOD CELLS; BODY FLUIDS; CARBOHYDRATES; CARBOXYLIC ACIDS; Cell Line; Cell Membrane - immunology; CONNECTIVE TISSUE CELLS; DAYS LIVING RADIOISOTOPES; Dextrans; ELECTRON CAPTURE RADIOISOTOPES; Endosomes; ENZYMES; Fundamental and applied biological sciences. Psychology; Fundamental immunology; GLOBINS; GLYCOSYL HYDROLASES; HEMOGLOBIN; HETEROCYCLIC ACIDS; HETEROCYCLIC COMPOUNDS; Histocompatibility antigens (hla, h-2 and other systems); Histocompatibility Antigens Class II - metabolism; HISTOCOMPATIBILITY COMPLEX; HYDROGEN COMPOUNDS; Hydrogen-Ion Concentration; HYDROLASES; INTERMEDIATE MASS NUCLEI; INTERNAL CONVERSION RADIOISOTOPES; IODINE 125; IODINE ISOTOPES; ISOTOPE APPLICATIONS; ISOTOPES; Kinetics; LEUKOCYTES; LYMPHOCYTES; Lysosomes; LYSOZYME; MACROPHAGES; Macrophages - immunology; MATERIALS; Mice; Mice, Inbred CBA; Molecular immunology; Molecules; Muramidase - immunology; Muramidase - metabolism; NUCLEI; O-GLYCOSYL HYDROLASES; ODD-EVEN NUCLEI; ORGANIC ACIDS; ORGANIC COMPOUNDS; ORGANIC NITROGEN COMPOUNDS; PEPTIDES; PH VALUE; PHAGOCYTES; PIGMENTS; POLYSACCHARIDES; Polysaccharides - pharmacology; PORPHYRINS; Protein Binding; PROTEINS; RADIOISOTOPES; RADIORECEPTOR ASSAY; SACCHARIDES; SOMATIC CELLS; T lymphocytes; TRACER TECHNIQUES; TRITIUM COMPOUNDS; Binding; Molecular processing; Peptides; Major histocompatibility system; Rodentia; Class II histocompatibility antigen; Molecular interaction; Antigen; Vertebrata; Mammalia; Mouse; PH; Polysaccharide
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.88.7.2740

The binding of immunogenic peptides to class II major histocompatibility molecules was examined at various pH values. We studied binding of peptides containing residues 52-61 from hen egg lysozyme (HEL) to I-Akon fixed peritoneal macrophages or to solubilized affinity-purified I-Ak. Optimum binding occurred at pH 5.5-6.0 with accelerated kinetics relative to pH 7.4; equilibrium binding was also higher at pH 5.5-6.0 than at 7.4. Similar enhancement at pH 5-6 was observed for the binding of hemoglobin-(64-76) to I-Ekand of ribonuclease-(41-61) to I-Ak. In contrast, the binding of HEL-(34-45) to I-Akwas minimally enhanced at acid pH. Dissociation of cell-associated or purified peptide-I-Akcomplexes was minimal between pH 5.5 and 7.4, with increased dissociation only at or below pH 4.0 [HEL-(46-61)] or pH 5.0 [HEL-(34-45)]. Thus, optimum peptide binding occurs at pH values similar to the endosomal environment, where the complexes appear to be formed during antigen processing. In addition, we examined the effect of a number of polysaccharides on the binding of peptide to I-Ak. None of these competed with the HEL peptide125I-labeled YE52-61 for binding to I-Ak. [3H]Dextran also failed to bind purified I-Ak. Polysaccharides do not appear to bind to class II major histocompatibility complex molecules, which explains the T-cell independence of polysaccharide antigens.