Abstract
Summary: Quantitative determinations of cryoglobulins (IgG, IgA, IgM, and C3) were performed by a laser nephelometry microtechnique on 250 serum samples from a group of pediatric patients suspected of having immune complex-mediated disorders. Approximately 50% of these samples were cryoglobulin positive. Patients with cryoglobulins were examined as three separate groups: systemic lupus erythematosus, presumptive autoimmune disorders, and chronic bacterial or viral infections. Nearly all of these patients have mixed cryoglobulins. The relation of cryoglobulinemia with serum hypocomplementemia and renal involvement was examined in a group of systemic lupus erythematosus patients. High levels of cryoglobulins were found in patients with hypocomplementemia and anti-DNA antibodies without clinical evidence of nephritis. Highly significant correlations were observed between C1q binding activity, presence of cryoglobulins, and serum hypocomplementemia in systemic lupus erythematosus patients. Only 60% of the cryoglobulin positive samples had immune complex demonstrable by C1q binding. Cryoglobulin analysis using the laser nephelometry microtechnique permits screening of pediatric patients for the presence of immune complex, permits detection of low levels of cryoglobulins, allows quantitative determination of the specific immunoglobulin classes in the precipitate, and requires only a very small amount of blood suitable for the pediatric population.
Speculation: Cryoglobulins may represent circulating immune complex (IC) in diseases where IC-mediated pathogenesis is implicated. In systemic lupus erythematosus, presence of anti-DNA antibodies, C1q binding activity and hypocomplementemia was accompanied by elevated cryoglobulins. It is possible that in these patients, the presence of IC detected by C1q binding activity is reflected by elevated cryoglobulins. When considering autoimmune diseases in general, cryoglobulin analysis via laser nephelometry may be more sensitive than C1q binding in detecting IC, some of which may not bind complement. This technique could easily be utilized as a screening, diagnostic, and perhaps prognostic tool for children with autoimmune diseases.
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Yang, L., Norman, M. & Doughty, R. A Micromethod for the Analysis of Cryoglobulins Via Laser Nephelometry: Evaluation and Comparison to C1q Binding Activity in Autoimmune Diseases in Pediatrics. Pediatr Res 14, 858–862 (1980). https://doi.org/10.1203/00006450-198007000-00003
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DOI: https://doi.org/10.1203/00006450-198007000-00003