title: Evaluation of Fc gamma receptor mediated T-cell activation by two purified CD3 x CD19 bispecific monoclonal antibodies with hybrid Fc domains.
abstract: Two bispecific monoclonal antibodies (BsAb), differing in H chain isotype combination, were made for treatment of B-cell leukaemia/lymphoma; QAI-2, CD3-mouse-IgG1 x CD19-mouse-IgG2a and QAI-3, CD3-mouse-IgG1 x CD19-mouse-IgG2b. Both purified BsAb proved equally effective for their ability to target pre-activated T cells towards CD19 positive tumour cells. In T-cell proliferation assays, the capacity of Fc gamma RIa (CD64), Fc gamma RIIa-R131 and Fc gamma RIIa-H131 (CD32) transfected fibroblasts was tested to present the BsAb. The BsAb combining mouse (m) IgG1 and mIgG2a promoted T-cell activation in combination with the Fc gamma RIa transfectant; the mIgG1-mIgG2b BsAb was only marginally active. Both BsAb could not induce T-cell activation when presented by either of the Fc gamma RIIa transfectants. Similar results were obtained using PBMC cultures, containing Fc gamma RIa+/Fc gamma RIIa+ monocytes as accessory cells. The importance of Fc gamma R-dependent BsAb-mediated T-cell activation emerged from experiments with T cells and CD19 positive B-cell lines, showing that cross-linking via CD19+ target cells alone did not induce T-cell proliferation. Therefore, BsAb with functionally different Fc domains represent alternative strategies in BsAb therapy, the efficacy of which deserves to be compared in vivo.
authors.affiliation: Department of Immunology, University Hospital Utrecht, The Netherlands.
authors.forename: I A
authors.initials: IA
authors.lastname: Haagen
authors.forename: A J
authors.initials: AJ
authors.lastname: Geerars
authors.forename: E J
authors.initials: EJ
authors.lastname: Bast
authors.forename: G C
authors.initials: GC
authors.lastname: de Gast
authors.forename: J G
authors.initials: JG
authors.lastname: van de Winkel
authors.forename: W B
authors.initials: WB
authors.lastname: de Lau
mesh_terms: D000818:Animals; D018033:Antibodies, Bispecific / Q000276:immunology*; D000915:Antibody Affinity; D000938:Antigen-Presenting Cells / Q000276:immunology; D018941:Antigens, CD19 / Q000276:immunology*; D017252:CD3 Complex / Q000276:immunology*; D003602:Cytotoxicity, Immunologic; D006801:Humans; D006825:Hybridomas; D007700:Kinetics; D008213:Lymphocyte Activation; D051379:Mice; D011485:Protein Binding; D017452:Receptors, IgG / Q000502:physiology*; D013601:T-Lymphocytes / Q000276:immunology*; D014162:Transfection
chemical_list: D018033:Antibodies, Bispecific; D018941:Antigens, CD19; D017252:CD3 Complex; D017452:Receptors, IgG