Cytosolic targeting of hen egg lysozyme gives rise to a short-lived protein presented by class I but not class II major histocompatibility complex molecules.
A way to study the role of intracellular trafficking of an antigen in its presentation to T cells is to target the antigen to various cell compartments of the antigen-presenting cells (APC) and compare the nature of the complexes associating major histocompatibility complex (MHC) molecules and antigenic peptides, expressed on the cell surface. MHC class I+ and MHC class II+ mouse L fibroblasts secreting hen egg lysozyme (HELs cells) or expressing HEL in their cytosol (HELc cells) were obtained after transfection with HEL cDNA and signal sequence-deleted HEL cDNA, respectively. HEL was evidenced in both HELs- and HELc-transfected cells and the former type of transfectant secreted a large amount of HEL. However, HEL produced in the cytosol exhibited a short half-life of less than 5 min. HEL-derived peptides could not be shown biochemically either in HELc- nor in HELs-transfected cells. We then studied the capacity of these cells to present HEL to HEL-specific class I- and class II-restricted T cells. Both cell types could be recognized by the HEL-specific MHC class I-restricted CTL clones. In contrast, MHC class II-HEL peptide complexes, recognized by HEL-specific helper T cell hybridomas, could be detected on MHC class II+ HELs- but not HELc-transfected cells. In vivo experiments showed, however, that HELc-transfected cells could provide host APC with HELc-derived peptides able to associate with MHC class II molecules. This was inferred from the capacity of MHC class II-HELc-transfected cells, unable by themselves to elicit any anti-HEL antibody response, to prime syngeneic and allogeneic mice against HEL. The priming was revealed by the induction of an antibody response after a boost with an amount of HEL unable itself to elicit an antibody response.
Calin-Laurens
V
V
Immunobiologie Moléculaire, UMR 49, CNRS-ENS Lyon, France.
Forquet
F
F
Mottez
E
E
Kanellopoulos
J
J
Godeau
F
F
Kourilsky
P
P
Gerlier
D
D
Rabourdin-Combe
C
C
D000595:Amino Acid Sequence; D000818:Animals; D000938:Antigen-Presenting Cells / Q000276:immunology*; D015152:Blotting, Northern; D015153:Blotting, Western; D002645:Chickens; D003600:Cytosol / Q000276:immunology / Q000378:metabolism; D015395:Histocompatibility Antigens Class I / Q000276:immunology*; D000949:Histocompatibility Antigens Class II / Q000276:immunology*; D006825:Hybridomas; D051379:Mice; D008969:Molecular Sequence Data; D009113:Muramidase / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D010446:Peptide Fragments / Q000276:immunology*; D011233:Precipitin Tests; D014176:Protein Biosynthesis; D021382:Protein Sorting Signals / Q000378:metabolism; D011994:Recombinant Proteins / Q000276:immunology / Q000378:metabolism; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology; D014158:Transcription, Genetic; D014162:Transfection
D015395:Histocompatibility Antigens Class I; D000949:Histocompatibility Antigens Class II; D010446:Peptide Fragments; D021382:Protein Sorting Signals; D011994:Recombinant Proteins; D009113:Muramidase