Abstract
When citrate plasma and serum of the same individual were tested simultaneously in the C1q-binding assay (C1qBA), binding levels in plasma were found to be 90-400% higher than in serum. The difference in 125I-Clq binding was due to the presence of fibrinogen in plasma. It was shown that complex formation between fibrinogen and 125I-Clq occurs and that this complex precipitates in the presence of polyethylene glycol, leading to the false positive results in the ClqBA. When heparin plasma was used to the assay, heparin itself also induced an increase in 125I-C1q binding that was not based on the presence of immune complexes. The effect of both fibrinogen and heparin could be inhibited by addition of protamine sulphate. Therefore, pretreatment of plasma with protamine sulphate makes it possible to use plasma samples for a reliable determination of C1q-binding levels. However, serum that is well clotted should be used preferentially.
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- HUNTER W. M., GREENWOOD F. C. Preparation of iodine-131 labelled human growth hormone of high specific activity. Nature. 1962 May 5;194:495–496. doi: 10.1038/194495a0. [DOI] [PubMed] [Google Scholar]
- Mancini G., Carbonara A. O., Heremans J. F. Immunochemical quantitation of antigens by single radial immunodiffusion. Immunochemistry. 1965 Sep;2(3):235–254. doi: 10.1016/0019-2791(65)90004-2. [DOI] [PubMed] [Google Scholar]
- McCluskey R. T., Hall C. L., Colvin R. B. Immune complex mediated diseases. Hum Pathol. 1978 Jan;9(1):71–84. doi: 10.1016/s0046-8177(78)80009-4. [DOI] [PubMed] [Google Scholar]
- Sobel A. T., Bokisch V. A., Müller-Eberhard H. J. C1q deviation test for the detection of immune complexes, aggregates of IgG, and bacterial products in human serum. J Exp Med. 1975 Jul 1;142(1):139–150. doi: 10.1084/jem.142.1.139. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Woodroffe A. J., Border W. A., Theofilopoulos A. N., Götze O., Glassock R. J., Dixon F. J., Wilson C. B. Detection of circulating immune complexes in patients with glomerulonephritis. Kidney Int. 1977 Oct;12(4):268–278. doi: 10.1038/ki.1977.111. [DOI] [PubMed] [Google Scholar]
- Yonemasu K., Stroud R. M. Structural studies on human Clq: non-covalent and covalent subunits. Immunochemistry. 1972 May;9(5):545–554. doi: 10.1016/0019-2791(72)90064-x. [DOI] [PubMed] [Google Scholar]
- Zubler R. H., Lambert P. H. Detection of immune complexes in human diseases. Prog Allergy. 1978;24:1–48. [PubMed] [Google Scholar]
- Zubler R. H., Lange G., Lambert P. H., Miescher P. A. Detection of immune complexes in unheated sera by modified 125I-Clq binding test. Effect of heating on the binding of Clq by immune complexes and application of the test to systemic lupus erythematosus. J Immunol. 1976 Jan;116(1):232–235. [PubMed] [Google Scholar]