title: Human CD4- CD8- alpha beta+ T cells express a functional T cell receptor and can be activated by superantigens.
abstract: The CD4 and CD8 molecules play an important role in the stimulation of T cells and in the process of thymic education. Most mature T cells express the alpha beta TCR and either CD4 or CD8; however, there is a small population of alpha beta+ TCR T cells that lack both CD4 and CD8. Little is known of the biology of the CD4- CD8- (double-negative) alpha beta+ TCR T cells or the nature of the Ag to which they may respond. These cells not only represent a novel population of T cells but also provide useful biologic tools to study the roles that CD4 and CD8 play in T cell activation. In this study we have addressed two questions. Firstly, whether CD4- CD8- alpha beta+ TCR T cells have functionally active TCR and, secondly, whether CD4 or CD8 is required for the activation of T cells by bacterial enterotoxins. Six double-negative alpha beta+ TCR T cell clones, propagated from two healthy donors, were challenged with a panel of nine bacterial enterotoxins. The V alpha and V beta usage of their TCR was determined by polymerase chain reaction. All of the CD4-CD8- clones proliferated in response to at least one of the enterotoxins, in a V beta-specific manner. The proliferative response of the CD4-CD8- alpha beta+ TCR T cell clones was similar in magnitude to that exhibited by CD4+ T cell clones of known V beta expression. These data clearly show that the CD4 and CD8 molecules are not required for the activation of untransformed human T cells by bacterial enterotoxins. Furthermore, these results indicate that CD4-CD8- alpha beta+ TCR T cells, normally present in all individuals, are not functionally silent, because they can be stimulated via their TCR. Their physiologic role, like that of gamma delta T cells, remains to be elucidated.
authors.affiliation: Charing Cross Sunley Research Centre, London, UK.
authors.forename: S
authors.initials: S
authors.lastname: Quaratino
authors.forename: G
authors.initials: G
authors.lastname: Murison
authors.forename: R E
authors.initials: RE
authors.lastname: Knyba
authors.forename: A
authors.initials: A
authors.lastname: Verhoef
authors.forename: M
authors.initials: M
authors.lastname: Londei
mesh_terms: D000942:Antigens, Bacterial / Q000276:immunology*; D001427:Bacterial Toxins / Q000276:immunology*; D002999:Clone Cells; D015332:Gene Rearrangement, alpha-Chain T-Cell Antigen Receptor; D015333:Gene Rearrangement, beta-Chain T-Cell Antigen Receptor; D006801:Humans; D066298:In Vitro Techniques; D008213:Lymphocyte Activation; D016693:Receptors, Antigen, T-Cell, alpha-beta / Q000235:genetics / Q000502:physiology*; D016176:T-Lymphocyte Subsets / Q000276:immunology*
chemical_list: D000942:Antigens, Bacterial; D001427:Bacterial Toxins; D016693:Receptors, Antigen, T-Cell, alpha-beta