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Construction of a series of chimeric antibodies (murine variable region and human constant region) derived from the murine antibody BIRR1, which recognizes intercellular adhesion molecule 1 (ICAM-1), has revealed differences in the relative binding abilities of the chimeric antibody to antigen. The chimeric antibodies show a ranking of their ability to compete with BIRR1 for antigen on the surface of cells with the order BIRR1 = cIgG1 (100%) > cIgG4 (30%) > cIgG2 (10%) as demonstrated by solid-phase competitive enzyme-linked immunosorbent assay. Papain digestion yielded Fab fragments that were purified to homogeneity. Competitive enzyme-linked immunosorbent assay showed that the chimeric and murine Fab binding constants were equivalent. A solution-phase binding assay (analyzed by size exclusion high performance liquid chromatography) between the intact mAbs and recombinant soluble ICAM-1 further established that the binding constants involving the Fab arms of the two antibodies were equivalent. In summary, the murine and chimeric anti-ICAM-1 antibodies bind cellular ICAM-1 with equivalent affinities but with differing avidities.


Journal article


The Journal of biological chemistry

Publication Date





13048 - 13055


Department of Biochemistry, Boehringer Ingelheim Pharmaceuticals, Inc., Ridgefield, Connecticut 06877-0368.


CHO Cells, Animals, Humans, Mice, Cell Adhesion Molecules, Intercellular Adhesion Molecule-1, Recombinant Fusion Proteins, Oligodeoxyribonucleotides, Antibodies, Monoclonal, Binding Sites, Antibody, Immunoglobulin Isotypes, Enzyme-Linked Immunosorbent Assay, Base Sequence, Molecular Sequence Data, Cricetinae, Immunoglobulin Fab Fragments