title: Selective T cell subset depletion with anti-CD4 and anti-CD8 intact ricin immunotoxins.
abstract: In the present study we have comparatively analysed the specific activity of a panel of immunotoxins (ITs) prepared by coupling Ricin to several monoclonal antibodies (MoAbs) directed against the CD3, CD4 and CD8 T cell membrane molecules. Peripheral blood and bone marrow mononuclear cells (PBMC and BMMC) were incubated with the different ITs for 2 h, in the presence of 0.1 M lactose, washed and subsequently stimulated with either phytohemagglutinin (PHA) or an anti-CD3 MoAb. Our results indicate that the proliferative response of PBMC to both stimuli was specifically inhibited (greater than 95%) by either anti-CD3 IT or a combination of anti-CD4 and CD8 ITs, at concentrations comparable to those previously used for ex vivo T cell depletion (300 ng/ml). When used individually at the same dose, anti-CD8 and anti-CD4 ITs inhibited the PHA-induced PBMC proliferative response 40 and 70% respectively. When either anti-CD4 or anti-CD8 IT-treated cells were activated with PHA and cultured for 14 days in the presence of IL-2, less than 2% of the blasts expressed the corresponding antigens as assessed by flow cytometry analysis. Similar results were observed when BMMC were treated with the different ITs. In contrast, the growth of CFU-GM was minimally affected (0-25% inhibition). Our data indicate that ITs directed against T cell subsets are highly active and specific reagents that may be potentially useful for pre-transplant bone marrow purging.
authors.affiliation: Department of Immunology, Hospital de la Princesa, Madrid, Spain.
authors.forename: M
authors.initials: M
authors.lastname: Izquierdo
authors.forename: M A
authors.initials: MA
authors.lastname: Balboa
authors.forename: A
authors.initials: A
authors.lastname: Figuera
authors.forename: M
authors.initials: M
authors.lastname: López-Botet
mesh_terms: D000945:Antigens, Differentiation, T-Lymphocyte / Q000276:immunology*; D001853:Bone Marrow / Q000276:immunology; D003114:Colony-Forming Units Assay; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D000922:Immunotoxins / Q000494:pharmacology*; D008213:Lymphocyte Activation / Q000187:drug effects; D008938:Mitosis / Q000187:drug effects; D009000:Monocytes / Q000276:immunology; D012276:Ricin / Q000494:pharmacology*; D013601:T-Lymphocytes / Q000187:drug effects / Q000276:immunology*
chemical_list: D000945:Antigens, Differentiation, T-Lymphocyte; D000922:Immunotoxins; D012276:Ricin