Eulitz M, Weiss D T, Solomon A
Department of Medicine, University of Tennessee Medical Center, Knoxville 37920.
Proc Natl Acad Sci U S A. 1990 Sep;87(17):6542-6. doi: 10.1073/pnas.87.17.6542.
Immunoglobulin- or multiple myeloma-associated amyloidosis has been distinguished by the tissue deposition of Congophilic, fibrillar protein consisting of light chains or light-chain fragments (AL amyloidosis). We now report the isolation and characterization of another form of immunoglobulin-associated amyloid obtained from a patient who had extensive systemic amyloidosis and in whom the amyloid deposits consisted not of light chains but rather of an unusual form of heavy chain. This component, isolated from splenic amyloid extracts, represented an internally deleted IgG1 heavy chain as evidenced by immunochemical, electrophoretic, and amino acid sequence analyses. A comparable immunoglobulin-related monoclonal protein, consisting only of IgG heavy chains, was present in the patient's urine. Based on serologic reactivity with a battery of anti-immunoglobulin antisera, these two immunoglobulin-related components were antigenically identical; however, when compared to normal IgG, both were deficient in Fc-associated gamma-chain determinants. The structural abnormality of the amyloid gamma-chain protein was further evidenced by SDS/PAGE and immuno-blotting analyses: An unusually low molecular mass of approximately 22 kDa was found for this material vs. the expected value of approximately 55 kDa for a normal gamma heavy chain. Despite the lack of certain Fc determinants, the amyloid and urinary heavy-chain proteins expressed the IgG1 subclass allotype marker G1m(a) located on the third constant region (CH3) domain of the internally deleted IgG1 heavy chains. That the amyloid protein contained an intact CH3 domain was established through amino acid sequence analyses of cyanogen bromide fragments and peptides generated by a lysine-specific protease. These studies also revealed that the gamma-chain amyloid protein contained the complete heavy-chain variable (VH) domain [including the diversity (DH) and joining (JH) segments] that was contiguous with the CH3 domain. The low molecular mass of the protein resulted from the total absence of the first (CH1), hinge, and second (CH2) heavy-chain constant regions. Such extensive CH deletions and the presence of a complete VH distinguish this amyloid-associated heavy chain from all other heretofore characterized gamma-heavy-chain disease proteins. This heavy-chain-related form of immunoglobulin-associated amyloidosis is tentatively designated AH amyloidosis.
免疫球蛋白或多发性骨髓瘤相关淀粉样变性的特征是由嗜刚果红的、由轻链或轻链片段组成的纤维状蛋白在组织中沉积（AL淀粉样变性）。我们现在报告从一名患有广泛系统性淀粉样变性的患者中分离并鉴定出另一种形式的免疫球蛋白相关淀粉样蛋白，该患者的淀粉样沉积物并非由轻链组成，而是由一种不寻常形式的重链组成。从脾脏淀粉样提取物中分离出的这种成分，经免疫化学、电泳和氨基酸序列分析证明是一种内部缺失的IgG1重链。患者尿液中存在一种仅由IgG重链组成的类似免疫球蛋白相关的单克隆蛋白。基于与一系列抗免疫球蛋白抗血清的血清学反应性，这两种免疫球蛋白相关成分在抗原上是相同的；然而，与正常IgG相比，两者都缺乏与Fc相关的γ链决定簇。SDS/PAGE和免疫印迹分析进一步证明了淀粉样γ链蛋白的结构异常：该物质的分子量异常低，约为22 kDa，而正常γ重链的预期值约为55 kDa。尽管缺乏某些Fc决定簇，但淀粉样蛋白和尿液重链蛋白表达了位于内部缺失的IgG1重链第三恒定区（CH3）结构域上的IgG1亚类同种异型标记G1m(a)。通过对溴化氰片段和赖氨酸特异性蛋白酶产生的肽进行氨基酸序列分析，确定淀粉样蛋白含有完整的CH3结构域。这些研究还表明，γ链淀粉样蛋白含有与CH3结构域相邻的完整重链可变（VH）结构域[包括多样性（DH）和连接（JH）片段]。该蛋白分子量低是由于完全缺乏第一（CH1）、铰链和第二（CH2）重链恒定区。如此广泛的CH缺失和完整VH结构域的存在将这种淀粉样相关重链与迄今为止所有其他已鉴定的γ重链病蛋白区分开来。这种重链相关形式的免疫球蛋白相关淀粉样变性暂定为AH淀粉样变性。
