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Antibody-directed liposomes Determination of affinity constants for soluble and liposome-bound antifluorescein |
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| Authors: | TD Heath RT Fraley J Bentz Voss EW Jr JN Herron D Papahadjopoulos |
| Institution: | 1. Cancer Research Institute and the Departments of Pharmacology, University of California at San Francisco, San Francisco, CA 94143 U.S.A.;2. Departments of Pharmacology, University of California at San Francisco, San Francisco, CA 94143 U.S.A.;3. Departments of Pharmacy and Pharmaceutical Chemistry, University of California at San Francisco, San Francisco, CA 94143 U.S.A.;4. Department of Microbiology, University of Illinois, Champaign Urbana, IL 61801 U.S.A. |
| Abstract: | We have used the binding of liposomes conjugated with antifluorescein antibody specific for fluorescein isothiocyanate-modified erythrocytes as a model for multivalent antigen-antibody interactions. We examined a series of liposome preparations which were conjugated to between 0 and 332 active antibodies per liposome. The antigen binding capacity and mean intrinsic affinity of the soluble and conjugated antibody were determined by fluorescence quenching of carboxyfluorescein. Liposome-cell interaction data were fitted with a Scatchard-type equation. Functional affinity of liposomes for cells was up to 1000-fold greater than the intrinsic affinity of the antibody for soluble ligand. Analysis for binding at high cell concentrations revealed that liposome-induced cell agglutination reduces the number of available binding sites per cell. |
| Keywords: | Liposome Fluorescein Antigen binding Antibody conjugate Liposome-cell interaction Fluorescence quenching (Human erythrocyte) |
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