title: CD4 molecules are associated with the antigen receptor complex on activated but not resting T cells.
abstract: To explore the relationship between CD4 and CD3/Ti on the T cell surface, we have studied a panel of Ag-specific Th cell lines and clones, as well as resting and mitogen-activated CD4+ cells. Our results show that exposure of Th cells to their specific antigenic stimuli, but not to irrelevant stimuli, induced the rapid disappearance of approximately 20 to 35% of CD3 and CD4 molecules. The modulation of these molecules was detected in less than 1 h, became maximal at 12 h, and recovered thereafter in parallel. Treatment of Th cells with anti-CD4 antibody prevented Ag-induced modulation of CD3, and treatment with anti-CD3 blocked modulation of CD4. In the absence of Ag, treatment of these cells with an antibody (WT-31) directed at a conformational determinant within CD3/Ti or with the combination of anti-CD3 antibody and goat anti-mouse Ig, also resulted in significant modulation of CD4. Similar treatment of PHA-activated CD4+ T cells with anti-CD3/Ti antibodies also induced CD4 modulation; however, the same antibodies failed to affect CD4 expression on fresh resting T cells. These results indicate that on activated, but not resting T cells, CD4 molecules can be physically associated with CD3/Ti. We postulate that this association is essential for efficient Th cell activation, and further that the ability of anti-CD4 antibodies to inhibit helper functions is due to their prevention of CD4-CD3/Ti interaction on the T cell surface.
authors.affiliation: Department of Pathology, Stanford University School of Medicine, CA 94305.
authors.forename: A
authors.initials: A
authors.lastname: Rivas
authors.forename: S
authors.initials: S
authors.lastname: Takada
authors.forename: J
authors.initials: J
authors.lastname: Koide
authors.forename: G
authors.initials: G
authors.lastname: Sonderstrup-McDevitt
authors.forename: E G
authors.initials: EG
authors.lastname: Engleman
mesh_terms: D000937:Antigen-Antibody Reactions; D000945:Antigens, Differentiation, T-Lymphocyte / Q000502:physiology*; D017252:CD3 Complex; D002462:Cell Membrane / Q000276:immunology; D007158:Immunologic Techniques; D008024:Ligands; D008213:Lymphocyte Activation; D046911:Macromolecular Substances; D011948:Receptors, Antigen, T-Cell / Q000502:physiology*; D013601:T-Lymphocytes / Q000276:immunology*; D013997:Time Factors
chemical_list: D000945:Antigens, Differentiation, T-Lymphocyte; D017252:CD3 Complex; D008024:Ligands; D046911:Macromolecular Substances; D011948:Receptors, Antigen, T-Cell