Gabriel A, Agnello V
J Clin Invest. 1977 May;59(5):990-1001. doi: 10.1172/JCI108722.
This study describes two sensitive, rapid, relatively simple, competitive inhibition radioimmunoassays for detecting immune complex. The tests are based on the inhibition of I125-Clq or I125-monoclonal rheumatoid factor (mRF) binding to an insoluble substrate, IgG-Sepharose. The assays can be performed in 5 h utilizing 10 micronl of serum. Heating of serum is not required and polyclonal rheumatoid factors do not interefere. With the two assays, a wide range of complexes of various size and complement fixing activity can be detected. The Clq test can detect complement fixing Ig complexes larger than 19S, while the mRF tests detect complexes of IgG as small as 8S irrespective of their complement fixing activity. Mouse, rabbit, and human aggregated IgG (agg IgG) can be detected in the Clq test, and human and rabbit agg IgG in the mRF test. As low as 4 microng/ml of isolated human agg IgG can be detected in the Clq test and 0.5 microng/ml in the rheumatoid factor test. Sensitivity is greater for mouse agg IgG. For pathologic sera which must be diluted to eliminate interfering factors, the sensitivity of the assay is approximately 10 times less. The Clq test showed marked inhibition by systemic lupus erythematosus sera with close correlation with CH50 levels and disease activity. The mRF test showed better correlation with rheumatoid arthritis sera. In addition, anionic macromolecules known to react with Clq and other Clq reactants that occur in pathologic sera such as the "low molecular weight" substances in systemic lupus erythematosus are also detected. These reactants are not detectable in the mRF test and can be eliminated in the Clq test by performing the test at higher ionic strength. The tests can be applied to the study of a variety of pathologic states where immune complexes appear to play a role.
本研究描述了两种用于检测免疫复合物的灵敏、快速、相对简单的竞争性抑制放射免疫分析法。这些检测基于I125 - Clq或I125 - 单克隆类风湿因子（mRF）与不溶性底物IgG - 琼脂糖结合的抑制作用。这些分析可在5小时内使用10微升血清完成。不需要加热血清，多克隆类风湿因子也不会产生干扰。通过这两种分析方法，可以检测到各种大小和补体固定活性的广泛复合物。Clq试验可检测大于19S的补体固定Ig复合物，而mRF试验可检测小至8S的IgG复合物，无论其补体固定活性如何。在Clq试验中可检测到小鼠、兔和人聚合IgG（agg IgG），在mRF试验中可检测到人和兔agg IgG。在Clq试验中可检测到低至4微克/毫升的分离人agg IgG，在类风湿因子试验中可检测到0.5微克/毫升。对小鼠agg IgG的敏感性更高。对于必须稀释以消除干扰因素的病理血清，该分析的敏感性约低10倍。Clq试验显示系统性红斑狼疮血清有明显抑制作用，与CH50水平和疾病活动密切相关。mRF试验与类风湿关节炎血清的相关性更好。此外，还可检测到已知与Clq反应的阴离子大分子以及病理血清中出现的其他与Clq反应的物质，如系统性红斑狼疮中的“低分子量”物质。这些反应物在mRF试验中无法检测到，并且可以通过在更高离子强度下进行Clq试验来消除。这些试验可应用于研究免疫复合物似乎起作用的各种病理状态。
