title: Cell-type-specific cytotoxicity of anti-CD4 and anti-CD8 ricin immunotoxins against human alloreactive T-cell clones.
abstract: Potent T-cell subset-directed immunotoxins (ITs) were generated by conjugating the anti-CD4 monoclonal antibody (MoAb) G17-2 and the anti-CD8 MoAb G10.1 to the ribosome-inhibitory protein, ricin. The cell-type-specific cytotoxicities of the generated ITs were evaluated at the clonal level using human alloreactive T-cell clones. The kinetics of anti-CD4 ricin-induced inactivation of protein synthesis in target CD4+ cloned T-cells was first order with no detectable lag period and a maximum rate of 0.07 logs per hour (t10 = 13.6 hours; first-order rate constant/K = 0.17 hr-1). The alloantigen specific lytic function of the CD4+ cytolytic T-cell clone JMAC28 was acutely sensitive to anti-CD4 ricin, and no residual lytic activity against allogeneic targets was detectable 24 hours after treatment with as little as 0.5 mmol/L anti-CD4 ricin. Notably, both anti-CD4 ricin and anti-CD8 ricin elicited a selective and dose-dependent inhibition of clonal proliferation of target T-cell clones with a maximum kill of greater than 3 logs at 5 nmol/L. No significant "bystander effects" were observed for non-target cells. Bone marrow progenitor cells CFU-GM, BFU-E, and CFU-GEMM were only minimally affected by either IT. We conclude that these ITs show considerable potential for effective depletion of T-cell subpopulations from allogeneic donor marrow grafts for clinical graft-versus-host disease (GVHD) prophylaxis.
authors.affiliation: Tumor Immunology Laboratory, University of Minnesota Health Sciences Center, Minneapolis.
authors.forename: F M
authors.initials: FM
authors.lastname: Uckun
authors.forename: D E
authors.initials: DE
authors.lastname: Myers
authors.forename: J A
authors.initials: JA
authors.lastname: Ledbetter
authors.forename: S L
authors.initials: SL
authors.lastname: Wee
authors.forename: D A
authors.initials: DA
authors.lastname: Vallera
mesh_terms: D000936:Antigen-Antibody Complex; D000945:Antigens, Differentiation, T-Lymphocyte / Q000276:immunology*; D001854:Bone Marrow Cells; D016026:Bone Marrow Transplantation / Q000276:immunology*; D015704:CD4 Antigens / Q000276:immunology*; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology; D016827:CD8 Antigens; D002470:Cell Survival; D002999:Clone Cells; D003602:Cytotoxicity, Immunologic; D005434:Flow Cytometry; D006412:Hematopoietic Stem Cells / Q000276:immunology; D007111:Immunity, Cellular; D000922:Immunotoxins / Q000008:administration & dosage*; D007376:Interleukin-2 / Q000494:pharmacology; D008213:Lymphocyte Activation; D012276:Ricin / Q000008:administration & dosage; D013601:T-Lymphocytes / Q000276:immunology*; D013997:Time Factors
chemical_list: D000936:Antigen-Antibody Complex; D000945:Antigens, Differentiation, T-Lymphocyte; D015704:CD4 Antigens; D016827:CD8 Antigens; D000922:Immunotoxins; D007376:Interleukin-2; D012276:Ricin