title: CD2 sets quantitative thresholds in T cell activation.
abstract: It has been proposed that CD2, which is highly expressed on T cells, serves to enhance T cell-antigen presenting cell (APC) adhesion and costimulate T cell activation. Here we analyzed the role of CD2 using CD2-deficient mice crossed with transgenic mice expressing a T cell receptor specific for lymphocytic choriomeningitis virus (LCMV)-derived peptide p33. We found that absence of CD2 on T cells shifted the p33-specific dose-response curve in vitro by a factor of 3-10. In comparison, stimulation of T cells in the absence of lymphocyte function-associated antigen (LFA)-1-intercellular adhesion molecule (ICAM)-1 interaction shifted the dose-response curve by a factor of 10, whereas absence of both CD2-CD48 and LFA-1-ICAM-1 interactions shifted the response by a factor of approximately 100. This indicates that CD2 and LFA-1 facilitate T cell activation additively. T cell activation at low antigen density was blocked at its very first steps, as T cell APC conjugate formation, TCR triggering, and Ca(2+) fluxes were affected by the absence of CD2. In vivo, LCMV-specific, CD2-deficient T cells proliferated normally upon infection with live virus but responded in a reduced fashion upon cross-priming. Thus, CD2 sets quantitative thresholds and fine-tunes T cell activation both in vitro and in vivo.
authors.affiliation: Basel Institute for Immunology, CH 4005 Basel, Switzerland. bachmann@bii.ch
authors.forename: M F
authors.initials: MF
authors.lastname: Bachmann
authors.forename: M
authors.initials: M
authors.lastname: Barner
authors.forename: M
authors.initials: M
authors.lastname: Kopf
mesh_terms: D000818:Animals; D015703:Antigens, CD / Q000502:physiology; D018801:CD2 Antigens / Q000502:physiology*; D000071178:CD48 Antigen; D002118:Calcium / Q000378:metabolism; D018799:Intercellular Adhesion Molecule-1 / Q000502:physiology; D008213:Lymphocyte Activation; D016169:Lymphocyte Function-Associated Antigen-1 / Q000502:physiology; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D011948:Receptors, Antigen, T-Cell / Q000502:physiology; D013601:T-Lymphocytes / Q000276:immunology*
chemical_list: D015703:Antigens, CD; D018801:CD2 Antigens; D000071178:CD48 Antigen; C000604066:Cd48 protein, mouse; D016169:Lymphocyte Function-Associated Antigen-1; D011948:Receptors, Antigen, T-Cell; D018799:Intercellular Adhesion Molecule-1; D002118:Calcium