Uckun F M, Fauci A S, Chandan-Langlie M, Myers D E, Ambrus J L
Department of Therapeutic Radiology-Radiation Oncology, University of Minnesota, Minneapolis 55455.
J Clin Invest. 1989 Nov;84(5):1595-608. doi: 10.1172/JCI114337.
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.
人高分子量B细胞生长因子（HMW - BCGF）（60kD）可刺激活化的正常B细胞、B细胞前体急性淋巴细胞白血病（BCP - ALL）细胞、毛细胞白血病（HCL）细胞、原淋巴细胞白血病（PLL）细胞以及慢性淋巴细胞白血病（CLL）细胞。采用125I标记的HMW - BCGF通过配体结合试验，以及使用抗HMW - BCGF受体单克隆抗体（MAb）BA - 5通过免疫荧光/流式细胞术和Scatchard分析，研究了慢性淋巴细胞白血病中白血病B细胞克隆群体上的人高分子量B细胞生长因子（HMW - BCGF）受体（R）的表达情况。HMW - BCGF受体表达与对HMW - BCGF的反应性之间存在高度相关性。60%的CLL病例组成性表达HMW - BCGF受体，并在[3H]TdR掺入试验以及集落试验中对HMW - BCGF表现出明显的增殖反应。同样，通过使用125I - HMW - BCGF的配体结合试验、[3H]TdR掺入试验以及与BA - 5单克隆抗体的反应性测定，发现HCL细胞、PLL细胞和活化的正常B细胞表达功能性HMW - BCGF受体。Scatchard分析表明，对HMW - BCGF有反应的CLL细胞上每个细胞约存在3000个HMW - BCGF受体，表观解离常数（Ka）值为4.6×10^7 M-1。最大程度刺激CLL细胞所需的HMW - BCGF浓度比半数最大受体占有率所需浓度低两到三个数量级，这表明只需占据一小部分HMW - BCGF受体就能刺激白血病CLL B细胞。将表面结合的125I - HMW - BCGF（60kD）与二价交联剂DTSSP交联到新鲜CLL细胞上的结合位点，鉴定出一种150kD的HMW - BCGF/HMW - BCGF受体复合物，提示受体蛋白的表观分子量为90kD。HMW - BCGF对克隆形成性CLL细胞的生长刺激作用不依赖于辅助细胞或共刺激因子。抗HMW - BCGF受体单克隆抗体BA - 5在克隆形成性CLL细胞水平破坏HMW - BCGF/HMW - BCGF受体相互作用，并在体外抑制HMW - BCGF刺激的CLL集落形成。据我们所知，本研究首次对B系CLL细胞上HMW - BCGF受体的表达、功能和结构进行了详细分析。
