title: Major histocompatibility class I presentation of soluble antigen facilitated by Mycobacterium tuberculosis infection.
abstract: Cell-mediated immune responses are essential for protection against many intracellular pathogens. For Mycobacterium tuberculosis (MTB), protection requires the activity of T cells that recognize antigens presented in the context of both major histocompatibility complex (MHC) class II and I molecules. Since MHC class I presentation generally requires antigen to be localized to the cytoplasmic compartment of antigen-presenting cells, it remains unclear how pathogens that reside primarily within endocytic vesicles of infected macrophages, such as MTB, can elicit specific MHC class I-restricted T cells. A mechanism is described for virulent MTB that allows soluble antigens ordinarily unable to enter the cytoplasm, such as ovalbumin, to be presented through the MHC class I pathway to T cells. The mechanism is selective for MHC class I presentation, since MTB infection inhibited MHC class II presentation of ovalbumin. The MHC class I presentation requires the tubercle bacilli to be viable, and it is dependent upon the transporter associated with antigen processing (TAP), which translocates antigenic peptides from the cytoplasm into the endoplasmic reticulum. The process is mimicked by Listeria monocytogenes and soluble listeriolysin, a pore-forming hemolysin derived from it, suggesting that virulent MTB may have evolved a comparable mechanism that allows molecules in a vacuolar compartment to enter the cytoplasmic presentation pathway for the generation of protective MHC class I-restricted T cells.
authors.affiliation: Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
authors.forename: R J
authors.initials: RJ
authors.lastname: Mazzaccaro
authors.forename: M
authors.initials: M
authors.lastname: Gedde
authors.forename: E R
authors.initials: ER
authors.lastname: Jensen
authors.forename: H M
authors.initials: HM
authors.lastname: van Santen
authors.forename: H L
authors.initials: HL
authors.lastname: Ploegh
authors.forename: K L
authors.initials: KL
authors.lastname: Rock
authors.forename: B R
authors.initials: BR
authors.lastname: Bloom
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000502:physiology; D000818:Animals; D000938:Antigen-Presenting Cells / Q000276:immunology; D002460:Cell Line; D004926:Escherichia coli / Q000276:immunology; D006412:Hematopoietic Stem Cells; D015395:Histocompatibility Antigens Class I / Q000096:biosynthesis / Q000276:immunology*; D000949:Histocompatibility Antigens Class II / Q000096:biosynthesis / Q000276:immunology; D007111:Immunity, Cellular; D007376:Interleukin-2 / Q000096:biosynthesis; D008089:Listeria monocytogenes / Q000276:immunology; D008264:Macrophages / Q000276:immunology; D051379:Mice; D008810:Mice, Inbred C57BL; D009169:Mycobacterium tuberculosis / Q000276:immunology*; D010047:Ovalbumin / Q000276:immunology; D013601:T-Lymphocytes / Q000276:immunology*; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology; D014376:Tuberculosis / Q000276:immunology*
chemical_list: D018528:ATP-Binding Cassette Transporters; D015395:Histocompatibility Antigens Class I; D000949:Histocompatibility Antigens Class II; D007376:Interleukin-2; D010047:Ovalbumin