Adhesion versus coreceptor function of CD4 and CD8: role of the cytoplasmic tail in coreceptor activity.
CD4 and CD8 play an important role in T-cell recognition and activation; however, their mechanisms of action are not well understood. We compare the effects of expressing CD4 and CD8 alpha either individually or together in a class II-restricted T-cell hybridoma. We also compare the effects of expressing truncated forms of CD4 or CD8 alpha that do not have a cytoplasmic tail and thus do not associate with the T-cell-specific tyrosine kinase p56lck, which has been implicated in T-cell activation. We demonstrate that, although CD4 and CD8 alpha can specifically enhance interleukin 2 secretion, maximal potentiation occurs with expression of CD4, which, unlike CD8, can bind to the same major histocompatibility complex protein as the T-cell receptor. Our data further indicate that the cytoplasmic tail and/or the associated p56lck are primarily significant for interleukin 2 secretion by the hybridomas we have examined when CD4 or CD8 can bind to the same major histocompatibility complex ligand as the T-cell receptor.
Miceli
M C
MC
Department of Medicine, Stanford University Medical Center, CA 94305-5111.
von Hoegen
P
P
Parnes
J R
JR
D000818:Animals; D000945:Antigens, Differentiation, T-Lymphocyte / Q000235:genetics / Q000276:immunology*; D015704:CD4 Antigens / Q000235:genetics / Q000276:immunology*; D016827:CD8 Antigens; D002448:Cell Adhesion; D003593:Cytoplasm / Q000276:immunology; D000949:Histocompatibility Antigens Class II / Q000276:immunology; D006825:Hybridomas / Q000276:immunology; D007328:Insulin / Q000494:pharmacology; D007376:Interleukin-2 / Q000096:biosynthesis; D007700:Kinetics; D007739:L Cells / Q000276:immunology; D051379:Mice; D011948:Receptors, Antigen, T-Cell / Q000276:immunology*; D013601:T-Lymphocytes / Q000276:immunology*; D014162:Transfection
D000945:Antigens, Differentiation, T-Lymphocyte; D015704:CD4 Antigens; D016827:CD8 Antigens; D000949:Histocompatibility Antigens Class II; D007328:Insulin; D007376:Interleukin-2; D011948:Receptors, Antigen, T-Cell