title: Bispecific anti-CD22/anti-CD3-ricin A chain immunotoxin is cytotoxic to Daudi lymphoma cells but not T cells in vitro and shows both A-chain-mediated and LAK-T-mediated killing.
abstract: We have generated a bispecific anti-CD22/anti-CD3 immunotoxin (IT) and determined whether it would exert both lymphokine-activated killer (LAK) T cell-mediated and ricin A chain (dgA)-mediated toxicity to Daudi tumor cells but not to T cells in vitro. One parental IT, Fab'-anti-CD22-dgA makes a potent immunotoxin for B cells, but not T cells, while the other, Fab'-anti-CD3-dgA, kills neither T nor B cells. Three mouse quadromas were generated and the bispecific Abs (BsAbs) were purified by double affinity chromatography. Two of the three purified BsAbs induced significant proliferation and IL-2 production in T cells. All three BsAbs induced LAK-T cell-mediated specific lysis of CD22+ Daudi cells. Two of the purified Ab were conjugated to dgA. Using a 51Cr release assay in the presence of LAK-T cells and Daudi target cells, the IC50s of the BsAbs were 3.5 x 10(-10) M and 9 x 10(-11) M, as compared to 2.1 x 10(-11) M and 3.2 x 10(-11) M, for their respective ITs. Hence, in the presence of LAK-T cells, the BsITs were 3- to 17-fold more cytotoxic than unconjugated BsAbs in 51Cr-release assays. Daudi cells were also treated in vitro with different mixtures of LAK-T cells, BsAbs, and BsITs and then adoptively transferred into SCID mice. As determined by the mean paralysis time of the recipients, in the presence of LAK-T cells the BsITs had impressive anti-tumor activity.
authors.affiliation: Department of Microbiology, University of Texas Southwestern Medical Center, Dallas 75235.
authors.forename: G L
authors.initials: GL
authors.lastname: Shen
authors.forename: J L
authors.initials: JL
authors.lastname: Li
authors.forename: E S
authors.initials: ES
authors.lastname: Vitetta
mesh_terms: D018033:Antibodies, Bispecific / Q000302:isolation & purification / Q000494:pharmacology; D000911:Antibodies, Monoclonal / Q000302:isolation & purification / Q000494:pharmacology; D015703:Antigens, CD; D000944:Antigens, Differentiation, B-Lymphocyte; D017252:CD3 Complex; D015815:Cell Adhesion Molecules; D003602:Cytotoxicity, Immunologic; D006801:Humans; D006825:Hybridomas / Q000276:immunology; D000922:Immunotoxins / Q000276:immunology / Q000494:pharmacology*; D007376:Interleukin-2 / Q000096:biosynthesis; D015979:Killer Cells, Lymphokine-Activated / Q000276:immunology; D037102:Lectins; D008213:Lymphocyte Activation; D008223:Lymphoma / Q000276:immunology / Q000628:therapy*; D012276:Ricin / Q000494:pharmacology*; D051918:Sialic Acid Binding Ig-like Lectin 2; D013601:T-Lymphocytes / Q000187:drug effects / Q000276:immunology; D014407:Tumor Cells, Cultured / Q000187:drug effects / Q000276:immunology
chemical_list: D018033:Antibodies, Bispecific; D000911:Antibodies, Monoclonal; D015703:Antigens, CD; D000944:Antigens, Differentiation, B-Lymphocyte; C497867:CD22 protein, human; D017252:CD3 Complex; D015815:Cell Adhesion Molecules; D000922:Immunotoxins; D007376:Interleukin-2; D037102:Lectins; D051918:Sialic Acid Binding Ig-like Lectin 2; D012276:Ricin