Zuckier L S, Chang C J, Scharff M D, Morrison S L
Department of Nuclear Medicine, Albert Einstein College of Medicine, Bronx, New York 10461, USA.
Cancer Res. 1998 Sep 1;58(17):3905-8.
Structural features that determine the differing rates of immunoglobulin catabolism are of great relevance to the engineering of immunologically active reagents. Sequences in the CH2 and CH3 region of IgG have been shown to regulate the rate of clearance through their interaction with FcRn. In an attempt to probe additional structural features that regulate antibody half-life, we have investigated two families of chimeric antibodies, composed of identical murine heavy and light antidansyl variable regions joined to human kappa light-chains and wild-type or shuffled human IgG heavy-chain constant regions. These antibodies were iodinated, and their clearance was studied in severe combined immunodeficient mice hosts by whole-body radioactivity measurements. Clearances of the wild-type and recombinant antibodies were biphasic. In a panel of immunoglobulins derived from IgG2 and IgG3, as successive domains were varied from gamma2 to gamma3, beta-phase half-life gradually decreased from 337.0 h to 70.6 h. Statistical analysis suggested that the composition of each of the three domains affected half-life, and no single region of the molecule by itself determined the rate of clearance. In the second panel of immunoglobulins derived from IgG1 and IgG4, the construct with the amino terminus portion of the molecule derived from IgG4, joined within the CH2 domain to the COOH terminus portion of IgG1, had a half-life paradoxically greater than either IgG1, or IgG4 (P < 0.012). All four IgG1/IgG4 constructs demonstrated presence of the concentration catabolism phenomenon, which is a unique hallmark of immunoglobulin catabolism. The contribution of all three constant region domains to immunoglobulin half-life may be due to distant conformational effects in addition to direct binding to protective receptors, and emphasizes the importance of distant sequences on the rate of immunoglobulin catabolism. Interesting possibilities regarding mechanisms controlling immunoglobulin metabolism are raised by the hybrid gamma4/gamma1 molecule with a half-life greater than either parental immunoglobulin. Understanding the relationships between the structure of these molecules and their clearance rate will further our ability to produce immunoglobulins with improved pharmacokinetic properties.
决定免疫球蛋白分解代谢速率差异的结构特征与免疫活性试剂的工程设计密切相关。已表明IgG的CH2和CH3区域中的序列通过与FcRn相互作用来调节清除率。为了探究调节抗体半衰期的其他结构特征，我们研究了两个嵌合抗体家族，它们由相同的鼠抗丹磺酰重链和轻链可变区与人类κ轻链以及野生型或重排的人类IgG重链恒定区连接而成。这些抗体被碘化，并通过全身放射性测量在严重联合免疫缺陷小鼠宿主中研究其清除情况。野生型和重组抗体的清除是双相的。在一组源自IgG2和IgG3的免疫球蛋白中，随着连续结构域从γ2变为γ3，β相半衰期从337.0小时逐渐降至70.6小时。统计分析表明，三个结构域中的每一个的组成都会影响半衰期，并且分子的任何单个区域本身都不能决定清除率。在源自IgG1和IgG4的第二组免疫球蛋白中，分子氨基末端部分源自IgG4且在CH2结构域内与IgG1的羧基末端部分连接的构建体，其半衰期反常地大于IgG1或IgG4（P < 0.012）。所有四种IgG1 / IgG4构建体都表现出浓度分解代谢现象，这是免疫球蛋白分解代谢的独特标志。所有三个恒定区结构域对免疫球蛋白半衰期的贡献可能不仅归因于与保护性受体的直接结合，还归因于远距离的构象效应，并强调了远距离序列对免疫球蛋白分解代谢速率的重要性。半衰期大于任何一种亲本免疫球蛋白的杂交γ4 /γ1分子提出了有关控制免疫球蛋白代谢机制的有趣可能性。了解这些分子的结构与其清除率之间的关系将提高我们生产具有改善药代动力学特性的免疫球蛋白的能力。
