title: Induction of alloantigen-specific hyporesponsiveness in human T lymphocytes by blocking interaction of CD28 with its natural ligand B7/BB1.
abstract: The specificity of T lymphocyte activation is determined by engagement of the T cell receptor (TCR) by peptide/major histocompatibility complexes expressed on the antigen-presenting cell (APC). Lacking costimulation by accessory molecules on the APC, T cell proliferation does not occur and unresponsiveness to subsequent antigenic stimulus is induced. The B7/BB1 receptor on APCs binds CD28 and CTLA-4 on T cells, and provides a costimulus for T cell proliferation. Here, we show that prolonged, specific T cell hyporesponsiveness to antigenic restimulation is achieved by blocking the interaction between CD28 and B7/BB1 in human mixed leukocyte culture (MLC). Secondary T cell proliferative responses to specific alloantigen were inhibited by addition to the primary culture of monovalent Fab fragments of anti-CD28 monoclonal antibody (mAb) 9.3, which block interaction of CD28 with B7/BB1 without activating T cells. Hypo-responsiveness was also induced in MLC by CTLA4Ig, a chimeric immunoglobulin fusion protein incorporating the extracellular domain of CTLA-4 with high binding avidity for B7/BB1. Cells previously primed could also be made hyporesponsive, if exposed to alloantigen in the presence of CTLA4Ig. Maximal hyporesponsiveness was achieved in MLC after 2 d of incubation with CTLA4Ig, and was maintained for at least 27 d after removal of CTLA4Ig. Accumulation of interleukin 2 (IL-2) and interferon gamma but not IL-4 mRNA was blocked by CTLA4Ig in T cells stimulated by alloantigen. Antigen-specific responses could be restored by addition of exogenous IL-2 at the time of the secondary stimulation. Addition to primary cultures of the intact bivalent anti-CD28 mAb 9.3, or B7/BB1+ transfected CHO cells or exogenous IL-2, abrogated induction of hyporesponsiveness by CTLA4Ig. These data indicate that interaction of CD28 with B7/BB1 during TCR engagement with antigen is required to maintain T cell competence and that blocking such interaction can result in a state of T cell hyporesponsiveness.
authors.affiliation: Division of Clinical Research, Fred Hutchinson Cancer Research Center, Seattle, Washington 98104.
authors.forename: P
authors.initials: P
authors.lastname: Tan
authors.forename: C
authors.initials: C
authors.lastname: Anasetti
authors.forename: J A
authors.initials: JA
authors.lastname: Hansen
authors.forename: J
authors.initials: J
authors.lastname: Melrose
authors.forename: M
authors.initials: M
authors.lastname: Brunvand
authors.forename: J
authors.initials: J
authors.lastname: Bradshaw
authors.forename: J A
authors.initials: JA
authors.lastname: Ledbetter
authors.forename: P S
authors.initials: PS
authors.lastname: Linsley
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D015703:Antigens, CD / Q000502:physiology*; D000945:Antigens, Differentiation, T-Lymphocyte / Q000502:physiology*; D000954:Antigens, Surface / Q000502:physiology*; D018122:B7-1 Antigen; D018106:CD28 Antigens; D015704:CD4 Antigens / Q000032:analysis; D016466:CHO Cells; D006224:Cricetinae; D006801:Humans; D007140:Immunoglobulin Fab Fragments / Q000276:immunology; D007376:Interleukin-2 / Q000494:pharmacology; D007519:Isoantigens / Q000276:immunology*; D051379:Mice; D013601:T-Lymphocytes / Q000276:immunology*; D013602:T-Lymphocytes, Cytotoxic / Q000502:physiology
chemical_list: D000911:Antibodies, Monoclonal; D015703:Antigens, CD; D000945:Antigens, Differentiation, T-Lymphocyte; D000954:Antigens, Surface; D018122:B7-1 Antigen; D018106:CD28 Antigens; D015704:CD4 Antigens; D007140:Immunoglobulin Fab Fragments; D007376:Interleukin-2; D007519:Isoantigens