title: Antibody-directed superantigen-mediated T-cell killing of myeloid leukaemic cell line cells.
abstract: Bacterial superantigens (SAgs) bound to MHC class II molecules on target cells are efficient activators of cytotoxic T cells expressing certain T cell receptor (TCR) Vbeta regions We described earlier that the specificity of the SAg Staphylococcus enterotoxin A (SEA) can be changed by introducing a D227A point mutation in the major MHC class II binding site and by genetically fusing the SEA mutant (SEAm) to protein A (PA). This SEAm-PA fusion protein can then be used to direct cytotoxic T cells to tumour cells coated with monoclonal antibodies (mAbs). In this communication, we tested the PA-SEAm fusion protein together with mAbs against the myeloid cell surface antigens CD13, CD15 and CD33. A SEA-reactive T cell line was used as effector cells against 10 different myeloid leukaemic cell lines. Optimal lysis of antigen positive leukaemic cells was obtained at a PA-SEAm concentration of 1 ng/ml and effector : target cell ratios of 15 : 1. No correlation between target cell sensitivity and the level of surface antigen expression could be seen. The 6 acute myeloid leukaemia (AML) cell lines tested appeared to be more sensitive than the 4 chronic myeloid leukaemia (CML) cell lines. The sensitivity of the AML cell line HL-60 could be improved further by stimulation with TNFalpha. This was accompanied by increased surface ICAM-1 expression whereas specific target molecule expression (CD13, CD33) was unchanged. This suggests that sensitivity to lysis is related to the leukaemic subtype and ICAM-1 expression but not to the tumour antigen density. Our results show that it is possible to direct cytotoxic T cells to myeloid leukaemia cells by using SAgs linked to mAbs, and encourage the construction and testing of a recombinant direct SAg-mAb fusion protein as a candidate drug for therapy of myeloid leukaemias.
authors.affiliation: Department of Clinical Immunology, University Hospital, Uppsala, Sweden.
authors.forename: C
authors.initials: C
authors.lastname: Gidlöf
authors.forename: B
authors.initials: B
authors.lastname: Carlson
authors.forename: M
authors.initials: M
authors.lastname: Dohlsten
authors.forename: T H
authors.initials: TH
authors.lastname: Tötterman
mesh_terms: D000911:Antibodies, Monoclonal / Q000276:immunology*; D000920:Antibody-Dependent Cell Cytotoxicity; D015703:Antigens, CD / Q000276:immunology; D015214:Antigens, Differentiation, Myelomonocytic / Q000276:immunology; D002460:Cell Line; D018922:HL-60 Cells; D006801:Humans; D007951:Leukemia, Myeloid / Q000276:immunology* / Q000473:pathology; D010641:Phenotype; D063268:Sialic Acid Binding Ig-like Lectin 3; D013268:Stimulation, Chemical; D018089:Superantigens / Q000276:immunology*; D013601:T-Lymphocytes / Q000276:immunology*; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology*; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
chemical_list: D000911:Antibodies, Monoclonal; D015703:Antigens, CD; D015214:Antigens, Differentiation, Myelomonocytic; C571163:CD33 protein, human; D063268:Sialic Acid Binding Ig-like Lectin 3; D018089:Superantigens; D014409:Tumor Necrosis Factor-alpha