caa a22 4500 469073985 CHVBK 20180323132930.0 cr unu---uuuuu 170328e19920901xx s 000 0 eng 10.1007/BF01741150 doi (NATIONALLICENCE)springer-10.1007/BF01741150 Blocked ricin-conjugated T cell immunotoxins: Effect of anti-CD6-blocked ricin on normal T cell function [Elektronische Daten] [Robert Rasmussen, Susan Counts, John Lambert, Albert Collinson] Summary: The biological properties of an immunotoxin composed of an anti-CD6 monoclonal antibody conjugated to whole ricin, which had been modified so that the galactose-binding sites of the B chain were blocked ("blocked ricin”), were examined. Treatment of peripheral blood lymphocytes with anti-CD6-blocked ricin for a 24-h period prevented T cell proliferation induced by phytohemagglutinin in a dose-dependent manner with concentrations causing 50% inhibition (IC50) ranging from 5 pM to 30 pM. In contrast, treatment with either blocked ricin alone or with a control immunotoxin prepared with a B-cell-lineage-restricted monoclonal antibody gave IC50 values of approximately 2 nM. Although shortening the duration of the anti-CD6-blocked ricin treatment to as little as 3 h had little significant effect on the observed inhibition, T cell viability experiments demonstrated that the magnitude of immunotoxin-induced killing after a given time period is significantly higher when the target cells become activated. Thus, from the initial concentration of cells treated with anti-CD6-blocked ricin placed in culture, 40%-45% viable cells remained after 2 days yet only 3%-9% remained if phorbol ester and Ca2+ ionophore were added; activation of T cells after mock treatment using blocked ricin plus nonconjugated anti-CD6 demonstrated that this effect was not the result of activation alone. The toxicity of anti-CD6-blocked ricin was also measured by inhibition of PHA-induced clonogenic growth of normal T cells. Continuous treatment of the cells using anti-CD6-blocked ricin at 0.1 nM resulted in a surviving fraction of about 3.5 × 10−3; when immunotoxin treatment was for 24 h or less, the surviving fraction was only about 10−1. As an indication of the unique specificity of anti-CD6-blocked ricin, immunotoxin pretreatment of potential responder cells prevented the generation of allogeneic cytolytic T lymphocytes in mixed lymphocyte cultures yet had little effect on the generation of interleukin-2-induced lymphokine-activated killer cell activity. We conclude that anti-CD6-blocked ricin demonstrates a cellular specificity and potency that make it a highly promising anti-T cell reagent. Springer-Verlag, 1992 CD6 nationallicence Immunotoxin nationallicence Blocked ricin nationallicence T cells nationallicence Rasmussen Robert Division of Tumor Immunology, Dana Farber Cancer Institute, Department of Pathology, Harvard Medical School, 44 Binney Street, 02 115, Boston, MA, USA aut Counts Susan Division of Tumor Immunology, Dana Farber Cancer Institute, Department of Pathology, Harvard Medical School, 44 Binney Street, 02 115, Boston, MA, USA aut Lambert John ImmunoGen Inc., 02 139, Cambridge, MA, USA aut Collinson Albert ImmunoGen Inc., 02 139, Cambridge, MA, USA aut Cancer Immunology, Immunotherapy Springer-Verlag 35/5(1992-09-01), 355-363 0340-7004 35:5<355 1992 35 262 https://doi.org/10.1007/BF01741150 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/BF01741150 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Rasmussen Robert Division of Tumor Immunology, Dana Farber Cancer Institute, Department of Pathology, Harvard Medical School, 44 Binney Street, 02 115, Boston, MA, USA aut NATIONALLICENCE 700 1- Counts Susan Division of Tumor Immunology, Dana Farber Cancer Institute, Department of Pathology, Harvard Medical School, 44 Binney Street, 02 115, Boston, MA, USA aut NATIONALLICENCE 700 1- Lambert John ImmunoGen Inc., 02 139, Cambridge, MA, USA aut NATIONALLICENCE 700 1- Collinson Albert ImmunoGen Inc., 02 139, Cambridge, MA, USA aut NATIONALLICENCE 773 0- Cancer Immunology, Immunotherapy Springer-Verlag 35/5(1992-09-01), 355-363 0340-7004 35:5<355 1992 35 262 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer