title: Modulation of CD4 by antigenic activation.
abstract: Cell surface expression of CD4, an invariant membrane glycoprotein, is characteristic of the MHC class II-restricted T cell helper/inducer subset. Although the specificity and restriction patterns of T lymphocytes are determined by the T cell receptor for antigen, CD4 might represent an additional "interaction" molecule that is required to strengthen the interaction between T cells, antigen, and antigen-presenting cells. In this manuscript, we have shown that the cell surface expression of CD4 is correlated with activation of T cells. Data presented in this paper have demonstrated, for the first time, that antigenic stimulation of human T cell clones caused a decrease in the expression of the CD4 marker (as well as to the CD3 marker) to about 50% of the constitutive level. As previously demonstrated, PMA caused modulation of CD4 and CD3, which suggested that phosphorylation by protein kinase C played a crucial role in the regulation of the expression of both markers. The parallel down-regulation of CD3 and CD4 after antigen stimulation suggested that both markers might be members of a multimolecular complex mediating T cell activation.
mesh_terms: D000945:Antigens, Differentiation, T-Lymphocyte; D000954:Antigens, Surface / Q000276:immunology*; D002454:Cell Differentiation; D004705:Endocytosis; D006801:Humans; D008213:Lymphocyte Activation; D013601:T-Lymphocytes / Q000276:immunology*
chemical_list: D000945:Antigens, Differentiation, T-Lymphocyte; D000954:Antigens, Surface