T84-intestinal epithelial exosomes bear MHC class II/peptide complexes potentiating antigen presentation by dendritic cells.
OBJECTIVE
Intestinal epithelial cells release antigen-presenting vesicles (exosomes) bearing major histocompatibility complex class II/peptide complexes stimulating specific immune responses in vivo. To characterize further the role of human epithelial exosomes in antigen presentation, their capacity to load antigenic peptides, bind immune target cells, and induce T-cell activation was analyzed in vitro.


METHODS
The capacity of exosomes derived from the HLA-DR4-expressing, intestinal epithelial cell line T84 to load the HLA-DR4-specific peptide (3)H-HSA 64-76 and to activate a HLA-DR4-restricted T-cell hybridoma was tested in the presence or absence of human monocyte-derived dendritic cells (DCs). Interaction of fluorescein isothiocyanate-labeled exosomes with T cells and DCs was analyzed by flow cytometry and confocal microscopy.


RESULTS
T84-derived exosomes, enriched in CD9, CD81, CD82, and A33 antigen, were capable of binding specifically human serum albumin (HSA) 64-76 peptide on HLA-DR4 molecules and of interacting preferentially with DCs. HSA-loaded exosomes were unable to activate the T-cell hybridoma directly but induced a productive T-cell activation through DCs. When HSA peptide was bound to exosomal HLA-DR4 molecules instead of in a soluble form, the threshold of peptide presentation by DCs was markedly decreased (x10(-3)).


CONCLUSIONS
Exosomes released by intestinal epithelial cells bear exogenous peptides complexed to major histocompatibility complex class II molecules and interact preferentially with DCs, strongly potentiating peptide presentation to T cells. Epithelial exosomes constitute a powerful link between luminal antigens and local immune cells by mediating the transfer of tiny amounts of luminal antigenic information and facilitating immune surveillance at mucosal surfaces.
Mallegol
Julia
J
INSERM U793, Paris, France.
Van Niel
Guillaume
G
Lebreton
Corinne
C
Lepelletier
Yves
Y
Candalh
Céline
C
Dugave
Christophe
C
Heath
Joan K
JK
Raposo
Graça
G
Cerf-Bensussan
Nadine
N
Heyman
Martine
M
D017951:Antigen Presentation / Q000502:physiology*; D002460:Cell Line; D003713:Dendritic Cells / Q000276:immunology / Q000502:physiology*; D005786:Gene Expression Regulation; D015804:HLA-DR4 Antigen / Q000235:genetics / Q000378:metabolism; D000949:Histocompatibility Antigens Class II / Q000502:physiology*; D006801:Humans; D006825:Hybridomas / Q000502:physiology; D007413:Intestinal Mucosa / Q000276:immunology*; D008213:Lymphocyte Activation / Q000276:immunology / Q000502:physiology; D011485:Protein Binding; D012709:Serum Albumin / Q000378:metabolism
D015804:HLA-DR4 Antigen; D000949:Histocompatibility Antigens Class II; D012709:Serum Albumin