CD8 expression allows T cell signaling by monomeric peptide-MHC complexes.
Physiologically, TCR signaling is unlikely to result from the cross-linking of TCR-CD3 complexes, given the low density of specific peptide-MHC complexes on antigen-presenting cells. We therefore have tested directly an alternative model for antigen recognition. We show that monomers of soluble peptide-MHC trigger Ca2+ responses in CD8alphabeta+ T cells. This response is not observed in CD8- T cells and when either the CD8:MHC or CD8:Lck interactions are prevented. This demonstrates that an intact CD8 coreceptor is necessary for effective TCR signaling in response to monomeric peptide-MHC molecules. We propose that this heterodimerization of TCR and CD8 by peptide-MHC corresponds to the physiological event normally involved during antigen-specific signal transduction.
Delon
J
J
Laboratoire d'Immunologie Cellulaire UMR CNRS 7627 CERVI, Paris, France.
Grégoire
C
C
Malissen
B
B
Darche
S
S
Lemaître
F
F
Kourilsky
P
P
Abastado
J P
JP
Trautmann
A
A
D000595:Amino Acid Sequence; D000818:Animals; D016827:CD8 Antigens / Q000737:chemistry / Q000378:metabolism*; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology* / Q000378:metabolism; D020013:Calcium Signaling; D019281:Dimerization; D006649:Histocompatibility Antigens / Q000378:metabolism; D006825:Hybridomas / Q000276:immunology; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck) / Q000378:metabolism; D051379:Mice; D008822:Mice, Transgenic; D010455:Peptides / Q000235:genetics / Q000276:immunology; D011948:Receptors, Antigen, T-Cell / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000276:immunology*; D014162:Transfection
D016827:CD8 Antigens; D006649:Histocompatibility Antigens; D010455:Peptides; D011948:Receptors, Antigen, T-Cell; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck)