title: Detection and characterization of human high molecular weight B cell growth factor receptors on leukemic B cells in chronic lymphocytic leukemia.
abstract: Human high molecular weight-B cell growth factor (HMW-BCGF) (60 kD) stimulates activated normal B cells, B cell precursor acute lymphoblastic leukemia (BCP-ALL) cells, hairy cell leukemia (HCL) cells, prolymphocytic leukemia (PLL) cells, and chronic lymphocytic leukemia (CLL) cells. The expression of human high molecular weight B cell growth factor (HMW-BCGF) receptors (R) on clonal populations of leukemic B cells in CLL was studied by ligand binding assays using 125I-labeled HMW-BCGF as well as by immunofluorescence/flow cytometry and Scatchard analyses using an anti-HMW-BCGF R monoclonal antibody (MAb), designated BA-5. There was a high correlation between HMW-BCGF R expression and responsiveness to HMW-BCGF. 60% of CLL cases constitutively expressed HMW-BCGF R and showed a marked proliferative response to HMW-BCGF in [3H]TdR incorporation assays as well as colony assays. Similarly, HCL cells, PLL cells, and activated normal B cells expressed functional HMW-BCGF R, as determined by ligand binding assays using 125I-HMW-BCGF, [3H]TdR incorporation assays, and reactivity with BA-5 MAb. Scatchard analyses indicated the existence of approximately 3,000 HMW-BCGF R/cell on HMW-BCGF responsive CLL cells with an apparent Ka value of 4.6 X 10(7) M-1. The concentrations of HMW-BCGF required for maximum stimulation of CLL cells were two to three orders of magnitude lower than those needed for half maximal receptor occupancy, indicating that only a small fraction of HMW-BCGF R need to be occupied to stimulate leukemic CLL B cells. Crosslinking of surface bound 125I-HMW-BCGF (60 kD) with the bivalent crosslinker DTSSP to its binding site on fresh CLL cells identified a 150-kD HMW-BCGF/HMW-BCGF R complex, suggesting an apparent molecular weight of 90 kD for the receptor protein. The growth stimulatory effects of HMW-BCGF on clonogenic CLL cells did not depend on accessory cells or costimulant factors. The anti-HMW-BCGF R monoclonal antibody BA-5 disrupted HMW-BCGF/HMW-BCGF R interactions at the level of clonogenic CLL cells and inhibited HMW-BCGF-stimulated CLL colony formation in vitro. To our knowledge, this study represents the first detailed analysis of expression, function, and structure of HMW-BCGF R on B lineage CLL cells.
authors.affiliation: Department of Therapeutic Radiology-Radiation Oncology, University of Minnesota, Minneapolis 55455.
authors.forename: F M
authors.initials: FM
authors.lastname: Uckun
authors.forename: A S
authors.initials: AS
authors.lastname: Fauci
authors.forename: M
authors.initials: M
authors.lastname: Chandan-Langlie
authors.forename: D E
authors.initials: DE
authors.lastname: Myers
authors.forename: J L
authors.initials: JL
authors.lastname: Ambrus
mesh_terms: D000368:Aged; D000911:Antibodies, Monoclonal; D001402:B-Lymphocytes / Q000276:immunology* / Q000473:pathology; D002455:Cell Division; D003432:Cross-Linking Reagents; D004247:DNA / Q000096:biosynthesis; D005260:Female; D005455:Fluorescent Antibody Technique; D006801:Humans; D015847:Interleukin-4 / Q000378:metabolism / Q000494:pharmacology; D007938:Leukemia / Q000378:metabolism / Q000473:pathology; D015451:Leukemia, Lymphocytic, Chronic, B-Cell / Q000276:immunology* / Q000473:pathology; D008297:Male; D008875:Middle Aged; D008970:Molecular Weight; D011869:Radioligand Assay; D019948:Receptors, Interleukin-4; D011975:Receptors, Mitogen / Q000032:analysis* / Q000502:physiology
chemical_list: D000911:Antibodies, Monoclonal; D003432:Cross-Linking Reagents; D019948:Receptors, Interleukin-4; D011975:Receptors, Mitogen; D015847:Interleukin-4; D004247:DNA