title: Evidence for an upper affinity threshold for anti-IgM-induced apoptosis in a human B-cell lymphoma.
abstract: The influence of ligand:receptor affinity on B-cell antigen receptor (BCR)-induced apoptosis in the IgM+ Burkitt lymphoma line, Ramos, was evaluated with a group of affinity-diverse murine monoclonal antibodies (MoAbs) specific for human B-cell IgM. The studies showed not only a minimal affinity threshold for the induction of apoptosis, but, interestingly, also a maximal affinity threshold above which increases in affinity were associated with diminished apoptosis. The lesser capacity of high-affinity MoAb to induce apoptosis was paralleled by a lesser capacity to induce receptor cross-linking. At high ligand concentration, high MoAb affinity was also associated with a diminished capacity to induce early protein tyrosine phosphorylation. The compromised capacity of two high-affinity MoAbs to trigger apoptosis may be, at least in part, explained by two separate phenomena that can impair the formation of mIgM cross-links: (1) more stable univalent binding and (2) a tendency for monogamous binding of both MoAb Fab to two Fab epitopes on mIgM. These in vitro studies suggest that the use of the highest affinity MoAbs for antireceptor immunotherapies that depend on receptor cross-linking might, on occasion, be contraindicated.
authors.affiliation: Department of Rheumatology, Hospital for Joint Diseases, New York, NY; the Department of Pathology, Kaplan Comprehensive Cancer Center, New York University School of Medicine, New York, NY, USA.
authors.forename: P K
authors.initials: PK
authors.lastname: Mongini
authors.forename: Q
authors.initials: Q
authors.lastname: Liu
authors.forename: M A
authors.initials: MA
authors.lastname: Vilensky
authors.forename: P F
authors.initials: PF
authors.lastname: Highet
authors.forename: J K
authors.initials: JK
authors.lastname: Inman
mesh_terms: D000818:Animals; D000888:Antibodies, Anti-Idiotypic / Q000494:pharmacology*; D000911:Antibodies, Monoclonal / Q000494:pharmacology*; D000915:Antibody Affinity; D000937:Antigen-Antibody Reactions; D017209:Apoptosis / Q000187:drug effects*; D001402:B-Lymphocytes / Q000276:immunology / Q000473:pathology*; D001666:Binding Sites, Antibody; D002051:Burkitt Lymphoma / Q000276:immunology / Q000473:pathology*; D006801:Humans; D007140:Immunoglobulin Fab Fragments / Q000276:immunology; D007075:Immunoglobulin M / Q000276:immunology*; D007152:Immunologic Capping; D007700:Kinetics; D051379:Mice; D010766:Phosphorylation; D011499:Protein Processing, Post-Translational; D014407:Tumor Cells, Cultured
chemical_list: D000888:Antibodies, Anti-Idiotypic; D000911:Antibodies, Monoclonal; D007140:Immunoglobulin Fab Fragments; D007075:Immunoglobulin M; C044203:anti-IgM