title: The Dendritic Cell Major Histocompatibility Complex II (MHC II) Peptidome Derives from a Variety of Processing Pathways and Includes Peptides with a Broad Spectrum of HLA-DM Sensitivity.
abstract: The repertoire of peptides displayed in vivo by MHC II molecules derives from a wide spectrum of proteins produced by different cell types. Although intracellular endosomal processing in dendritic cells and B cells has been characterized for a few antigens, the overall range of processing pathways responsible for generating the MHC II peptidome are currently unclear. To determine the contribution of non-endosomal processing pathways, we eluted and sequenced over 3000 HLA-DR1-bound peptides presented in vivo by dendritic cells. The processing enzymes were identified by reference to a database of experimentally determined cleavage sites and experimentally validated for four epitopes derived from complement 3, collagen II, thymosin β4, and gelsolin. We determined that self-antigens processed by tissue-specific proteases, including complement, matrix metalloproteases, caspases, and granzymes, and carried by lymph, contribute significantly to the MHC II self-peptidome presented by conventional dendritic cells in vivo. Additionally, the presented peptides exhibited a wide spectrum of binding affinity and HLA-DM susceptibility. The results indicate that the HLA-DR1-restricted self-peptidome presented under physiological conditions derives from a variety of processing pathways. Non-endosomal processing enzymes add to the number of epitopes cleaved by cathepsins, altogether generating a wider peptide repertoire. Taken together with HLA-DM-dependent and-independent loading pathways, this ensures that a broad self-peptidome is presented by dendritic cells. This work brings attention to the role of "self-recognition" as a dynamic interaction between dendritic cells and the metabolic/catabolic activities ongoing in every parenchymal organ as part of tissue growth, remodeling, and physiological apoptosis.
authors.affiliation: From the Departments of Pathology and.
authors.forename: Cristina C
authors.initials: CC
authors.lastname: Clement
authors.affiliation: the Departments of Pathology and.
authors.forename: Aniuska
authors.initials: A
authors.lastname: Becerra
authors.affiliation: the Departments of Pathology and.
authors.forename: Liusong
authors.initials: L
authors.lastname: Yin
authors.affiliation: From the Departments of Pathology and.
authors.forename: Valerio
authors.initials: V
authors.lastname: Zolla
authors.affiliation: From the Departments of Pathology and.
authors.forename: Liling
authors.initials: L
authors.lastname: Huang
authors.affiliation: the School of Medicine, University of Piemonte Orientale, 28100 Novara, Italy.
authors.forename: Simone
authors.initials: S
authors.lastname: Merlin
authors.affiliation: From the Departments of Pathology and; the School of Medicine, University of Piemonte Orientale, 28100 Novara, Italy.
authors.forename: Antonia
authors.initials: A
authors.lastname: Follenzi
authors.affiliation: Biochemistry and Molecular Pharmacology and; the Proteomics and Mass Spectrometry Facility, University of Massachusetts Medical School, Worcester, Massachusetts 01655, and.
authors.forename: Scott A
authors.initials: SA
authors.lastname: Shaffer
authors.affiliation: the Departments of Pathology and; Biochemistry and Molecular Pharmacology and.
authors.forename: Lawrence J
authors.initials: LJ
authors.lastname: Stern
authors.affiliation: From the Departments of Pathology and; Microbiology and Immunology, Albert Einstein College of Medicine, New York, New York 10461,. Electronic address: laura.santambrogio@einstein.yu.edu.
authors.forename: Laura
authors.initials: L
authors.lastname: Santambrogio
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002478:Cells, Cultured; D024043:Collagen Type II / Q000737:chemistry / Q000378:metabolism; D003176:Complement C3 / Q000737:chemistry / Q000378:metabolism; D003713:Dendritic Cells / Q000737:chemistry / Q000378:metabolism*; D018260:Gelsolin / Q000737:chemistry / Q000378:metabolism; D015798:HLA-DR1 Antigen / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D008196:Lymph / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry / Q000378:metabolism*; D011485:Protein Binding; D020543:Proteome / Q000737:chemistry / Q000378:metabolism*; D040901:Proteomics; D015398:Signal Transduction; D013947:Thymosin / Q000737:chemistry / Q000378:metabolism; D000099201:Thymosin beta(4)
chemical_list: D024043:Collagen Type II; D003176:Complement C3; D018260:Gelsolin; D015798:HLA-DR1 Antigen; D010455:Peptides; D020543:Proteome; D013947:Thymosin; D000099201:Thymosin beta(4)
keywords: antigen presentation; antigen processing; dendritic cell; immunological tolerance; lymph; major histocompatibility complex (MHC); proteomics; tolerance