title: T-cell stimulation and cytokine release induced by staphylococcal enterotoxin A (SEA) and the SEAD227A mutant.
abstract: Previous work demonstrated that human cytotoxic T cells activated by superantigens can lyse major histocompatibility complex (MHC) class II-positive target cells as well as MHC class II-negative tumour cells coated with conjugates of monoclonal antibodies and superantigens. In order to decrease MHC class II affinity, and therefore unwanted binding of the superantigen staphylococcal enterotoxin A (SEA) to MHC class II molecules, a point mutation was introduced into the SEA gene. This mutation (SEAD227A) resulted in an approximately 3-log reduction of affinity to human leucocyte antigen (HLA)-DR, but cytotoxicity mediated by this mutant superantigen towards antibody-labelled tumour cells is as efficient as cytotoxicity mediated by the native superantigen. We therefore compared the T-cell activating potency of native and mutated SEA. Our data show that SEAD227A is 4- to 5-log less effective than native SEA when activation of resting T cells is assayed in terms of blast formation, expression of cell surface activation markers and cytokine release. Furthermore, presenting either SEA or SEAD227A to MHC class II-negative mononuclear cells by MHC class II-negative tumour cells did not result in significant blast formation of T cells, up-regulation of CD25 or cytokine release. This suggests that lysis of MHC class II-negative tumour cells is efficiently induced by monoclonal antibody targeted superantigen, while activation of resting T cells requires additional co-stimulatory signals.
authors.affiliation: Children's University Hospital, Department of Oncology/Haematology, Tübingen, Germany.
authors.forename: U
authors.initials: U
authors.lastname: Holzer
authors.forename: T
authors.initials: T
authors.lastname: Orlikowsky
authors.forename: C
authors.initials: C
authors.lastname: Zehrer
authors.forename: W
authors.initials: W
authors.lastname: Bethge
authors.forename: M
authors.initials: M
authors.lastname: Dohlsten
authors.forename: T
authors.initials: T
authors.lastname: Kalland
authors.forename: D
authors.initials: D
authors.lastname: Niethammer
authors.forename: G E
authors.initials: GE
authors.lastname: Dannecker
mesh_terms: D018929:Cell Culture Techniques; D016207:Cytokines / Q000378:metabolism*; D003602:Cytotoxicity, Immunologic; D004768:Enterotoxins / Q000235:genetics / Q000276:immunology*; D006681:HLA-D Antigens / Q000032:analysis; D006801:Humans; D008213:Lymphocyte Activation / Q000276:immunology*; D017354:Point Mutation; D018089:Superantigens / Q000276:immunology; D013601:T-Lymphocytes / Q000276:immunology*; D014407:Tumor Cells, Cultured
chemical_list: D016207:Cytokines; D004768:Enterotoxins; D006681:HLA-D Antigens; D018089:Superantigens; C026066:enterotoxin A, Staphylococcal