title: H2-M3-restricted T cells participate in the priming of antigen-specific CD4+ T cells.
abstract: H2-M3-restricted CD8+ T cells provide early protection against bacterial infections. In this study, we demonstrate that activated H2-M3-restricted T cells provide early signals for efficient CD4+ T cell priming. C57BL/6 mice immunized with dendritic cells coated with the MHC class II-restricted listeriolysin O peptide LLO(190-201) (LLO) generated CD4+ T cells capable of responding to Listeria monocytogenes (LM) infection. Inclusion of a H2-M3-restricted formylated peptide fMIGWII (fMIG), but not MHC class Ia-restricted peptides, during immunization with LLO significantly increased IFN-gamma-producing CD4+ T cell numbers, which was associated with increased protection against LM infection. Studies with a CD4+ T cell-depleting mAb indicate that the reduction in bacterial load in fMIG plus LLO immunized mice is likely due to augmented numbers of LLO-specific CD4+ T cells, generated with the help of H2-M3-restricted CD8+ T cells. We also found that augmentation of LLO-specific CD4+ T lymphocytes with H2-M3-restricted T cells requires presentation of LLO and fMIG by the same dendritic cells. Interestingly, the augmented CD4+ T cell response generated with fMIG also increased primary LM-specific responses by MHC class Ia-restricted CD8 T cells. Coimmunization with LLO and fMIG also increases the number of memory Ag-specific CD4+ T cells. We also demonstrate that CD8 T cells restricted to another MHC class Ib molecule, Qa-1, whose human equivalent is HLA-E, are also able to enhance Ag-specific CD4+ T cell responses. These results reveal a novel function for H2-M3- and Qa-1-restricted T cells; provision of help to CD4+ Th cells during the primary response.
authors.affiliation: Department of Microbiology and Immunology, University of British Columbia, Vancouver, British Columbia, Canada.
authors.forename: Michael T
authors.initials: MT
authors.lastname: Chow
authors.forename: Salim
authors.initials: S
authors.lastname: Dhanji
authors.forename: Jennifer
authors.initials: J
authors.lastname: Cross
authors.forename: Pauline
authors.initials: P
authors.lastname: Johnson
authors.forename: Hung-Sia
authors.initials: HS
authors.lastname: Teh
mesh_terms: D019264:Adoptive Transfer; D000818:Animals; D017951:Antigen Presentation / Q000276:immunology*; D001424:Bacterial Infections / Q000517:prevention & control / Q000628:therapy; D001427:Bacterial Toxins / Q000276:immunology; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology*; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology; D003713:Dendritic Cells / Q000276:immunology / Q000637:transplantation; D006360:Heat-Shock Proteins / Q000276:immunology; D006460:Hemolysin Proteins / Q000276:immunology; D015395:Histocompatibility Antigens Class I / Q000276:immunology*; D007114:Immunization / Q000379:methods*; D008089:Listeria monocytogenes; D051379:Mice; D008810:Mice, Inbred C57BL; D037182:T-Cell Antigen Receptor Specificity; D013601:T-Lymphocytes / Q000276:immunology*
chemical_list: D001427:Bacterial Toxins; C078177:H2-M3 antigen; D006360:Heat-Shock Proteins; D006460:Hemolysin Proteins; D015395:Histocompatibility Antigens Class I; C032907:Q surface antigens; C038705:hlyA protein, Listeria monocytogenes