title: Dissection of the HLA-DR4 peptide repertoire in endocrine epithelial cells: strong influence of invariant chain and HLA-DM expression on the nature of ligands.
abstract: Class II MHC (MHC II) expression is restricted to professional APCs and thymic epithelium but it also occurs in the epithelial cells of autoimmune organs which are the unique targets of the CD4 autoreactive T cells in endocrine autoimmune diseases. This specificity is presumably conditioned by an epithelium-specific peptide repertoire associated to MHC II at the cell surface. MHC II expression and function is dependent on the action of two main chaperones, invariant chain (Ii) and DM, whose expression is coregulated with MHC II. However, there is limited information about the in vivo expression levels of these molecules and uncoordinated expression has been demonstrated in class II-positive epithelial cells that may influence the MHC-associated peptide repertoires and the outcome of the autoimmune response. We have examined the pool of peptides associated to DR4 molecules expressed by a neuroendocrine epithelial cell and the consequences of Ii and DM coexpression. The RINm5F rat insulinoma cell line was transfected with HLA-DRB1*0401, Ii, and DM molecules in four different combinations: RIN-DR4, -DR4Ii, -DR4DM, and -DR4IiDM. The analysis of the peptide repertoire and the identification of the DR4 naturally processed ligands in each transfected cell were achieved by mass spectrometry. The results demonstrate that 1) the expression of Ii and DM affected the DR4 peptide repertoires by producing important variations in their content and in the origin of peptides; 2) these restrictions affected the stability and sequence of the peptides of each repertoire; and 3) Ii and DM had both independent and coordinate effects on these repertoires.
authors.affiliation: Immunology Unit and Institute of Biotechnology and Biomedicine (IBB), Universitat Autònoma de Barcelona, Campus de Bellaterra, Barcelona, Spain.
authors.forename: Aura
authors.initials: A
authors.lastname: Muntasell
authors.forename: Montserrat
authors.initials: M
authors.lastname: Carrascal
authors.forename: Iñaki
authors.initials: I
authors.lastname: Alvarez
authors.forename: Laurence
authors.initials: L
authors.lastname: Serradell
authors.forename: Peter
authors.initials: P
authors.lastname: van Veelen
authors.forename: Frank A W
authors.initials: FA
authors.lastname: Verreck
authors.forename: Frits
authors.initials: F
authors.lastname: Koning
authors.forename: Joaquín
authors.initials: J
authors.lastname: Abian
authors.forename: Dolores
authors.initials: D
authors.lastname: Jaraquemada
mesh_terms: D000818:Animals; D000944:Antigens, Differentiation, B-Lymphocyte / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D004703:Endocrine System / Q000276:immunology / Q000378:metabolism*; D004848:Epithelium / Q000378:metabolism; D006681:HLA-D Antigens / Q000378:metabolism*; D006684:HLA-DR Antigens / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D015804:HLA-DR4 Antigen / Q000235:genetics / Q000378:metabolism*; D059811:HLA-DRB1 Chains; D000949:Histocompatibility Antigens Class II / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D008024:Ligands; D051379:Mice; D010455:Peptides / Q000302:isolation & purification / Q000378:metabolism*; D011487:Protein Conformation; D051381:Rats; D014162:Transfection
chemical_list: D000944:Antigens, Differentiation, B-Lymphocyte; D006681:HLA-D Antigens; C084245:HLA-DM antigens; D006684:HLA-DR Antigens; D015804:HLA-DR4 Antigen; D059811:HLA-DRB1 Chains; C553505:HLA-DRB1*04:01 antigen; D000949:Histocompatibility Antigens Class II; D008024:Ligands; D010455:Peptides; C045084:invariant chain