Ely P, Wallace P K, Givan A L, Graziano R F, Guyre P M, Fanger M W
Department of Medicine, Dartmouth Medical School, Lebanon, NH 03756, USA.
Blood. 1996 May 1;87(9):3813-21.
To show that macrophages can be effectively targeted against malignant B cells, bispecific antibodies (BsAb) were constructed from two antibodies having specificity for the high-affinity Fc receptor for IgG (Fc gamma RI/CD64) and the B-cell differentiation antigens CD19 and CD37. Using a flow cytometry-based assay and confocal imaging, we show that these constructs mediated significant phagocytosis of B lymphocytes by macrophages that could be enhanced with interferon gamma (IFN gamma) and IFN gamma in combination with macrophage colony-stimulating factor. BsAb-dependent phagocytosis was triggered through Fc gamma RI and could be blocked only by using F(ab')2 fragments from the parent molecule or by cross-linking Fc gamma RI. BsAb-dependent phagocytosis was not blocked by antibodies to the other Fc receptors, Fc gamma RII and Fc gamma RIII. Because these antibody constructs bind to an epitope outside the Fc gamma RI ligand binding site, we show that autologous serum, polyclonal IgG, and monomeric IgG1 did not block BsAb-dependent phagocytosis, whereas autologous serum and the IgG fractions blocked parent molecule monoclonal antibody-dependent phagocytosis due to the avid binding of monomeric IgG to Fc gamma RI. Finally, BsAb-mediated phagocytosis was effective against the malignant B cells of patients with mantle cell lymphoma, prolymphocytic leukemia, and chronic lymphocytic leukemia. Based on these studies, we propose that BsAbs may provide an effective means of immunomodulation for patients with B-cell malignancies.
为了证明巨噬细胞能够有效地靶向恶性B细胞，构建了双特异性抗体（BsAb），其由两种分别对IgG的高亲和力Fc受体（FcγRI/CD64）以及B细胞分化抗原CD19和CD37具有特异性的抗体组成。通过基于流式细胞术的检测和共聚焦成像，我们发现这些构建体介导巨噬细胞对B淋巴细胞的显著吞噬作用，干扰素γ（IFNγ）以及IFNγ与巨噬细胞集落刺激因子联合使用可增强这种吞噬作用。依赖BsAb的吞噬作用通过FcγRI触发，并且仅通过使用亲本分子的F(ab')2片段或交联FcγRI才能被阻断。依赖BsAb的吞噬作用不会被针对其他Fc受体FcγRII和FcγRIII的抗体阻断。由于这些抗体构建体结合于FcγRI配体结合位点之外的表位，我们发现自体血清、多克隆IgG和单体IgG1不会阻断依赖BsAb的吞噬作用，而自体血清和IgG组分却会阻断亲本分子单克隆抗体依赖的吞噬作用，这是因为单体IgG与FcγRI的avid结合。最后，BsAb介导的吞噬作用对套细胞淋巴瘤、原淋巴细胞白血病和慢性淋巴细胞白血病患者的恶性B细胞有效。基于这些研究，我们提出BsAbs可能为B细胞恶性肿瘤患者提供一种有效的免疫调节手段。
