title: Distribution of endocytosed molecules to intracellular acidic environments correlates with immunotoxin activity.
abstract: We have investigated the internalization to low pH intracellular compartments of transferrin (Tfn), diphtheria toxin (DT) and of anti-cell surface antibodies (MAb) by a cytofluorometric assay based on low pH quenching of fluorescein (FITC) emission. FITC-labelled Tfn, anti-CD3, anti-CD5 and anti-Thy 1.2 MAb internalization resulted in a progressively lower FITC quenching effect. Following internalization, a distinction could be made between molecules that enter low pH compartments without undergoing intracellular degradation (e.g., Tfn, anti-CD3 MAb) and molecules that are internalized through low pH organelles and are then degraded within the cell (e.g., DT). A strict correlation was observed between quenching of internalized FITC-protein fluorescent emission and the cytotoxic activity of DT-based immunotoxins (IT).
authors.affiliation: Istituto di Scienze Immunologiche, University of Verona, Italy.
authors.forename: R
authors.initials: R
authors.lastname: Chignola
authors.forename: M
authors.initials: M
authors.lastname: Colombatti
authors.forename: L
authors.initials: L
authors.lastname: Dell'Arciprete
authors.forename: C
authors.initials: C
authors.lastname: Candiani
authors.forename: G
authors.initials: G
authors.lastname: Tridente
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000493:pharmacokinetics; D002460:Cell Line; D004167:Diphtheria Toxin / Q000493:pharmacokinetics*; D004705:Endocytosis / Q000502:physiology*; D005434:Flow Cytometry; D016650:Fluorescein-5-isothiocyanate; D005452:Fluoresceins; D006801:Humans; D006863:Hydrogen-Ion Concentration; D000922:Immunotoxins / Q000493:pharmacokinetics*; D007424:Intracellular Fluid / Q000378:metabolism*; D051379:Mice; D051381:Rats; D013861:Thiocyanates; D014168:Transferrin / Q000493:pharmacokinetics*
chemical_list: D000911:Antibodies, Monoclonal; D004167:Diphtheria Toxin; D005452:Fluoresceins; D000922:Immunotoxins; D013861:Thiocyanates; D014168:Transferrin; D016650:Fluorescein-5-isothiocyanate