Immunoquantitation of Hageman factor in urine and plasma of children with nephrotic syndrome.

Children with nephrotic syndrome frequently have decreased plasma levels of Hageman factor (factor XII). Studies were designed to determine whether this finding results primarily from a loss of Hageman factor in the urine or is related to an alteration in the Hageman factor protein itself. A monospecific anti-Hageman factor goat antibody was prepared and used for quantitative measurements of Hageman factor in urine and plasma by a radial immunodiffusion method. Samples of 24 hr urine collections from 14 children with nephrotic syndrome were examined by this immunoassay technique; no Hageman factor was detected in the urine in 13/14 patients. Comparative studies using plasma from the nephrotic syndrome patients and nine normal controls demonstrated: (1) a significantly reduced level of Hageman ACT in the nephrotic syndrome patients (p < 0.001); (2) a reduction to a lesser degree of the levels of CRM in the same group (p < 0.001); and (3) a significantly increased CRM/ACT ratio in the plasma of the patients with nephrotic syndrome (p < 0.01) indicating partial inactivation of the Hageman factor enzymatic function. However, no inhibitory activity to added Hageman factor could be detected in the plasma or urine of the patients. These findings indicate that the decreased plasma Hageman factor activity that accompanies the nephrotic syndrome cannot be adequately explained by simple urinary loss of Hageman factor as has previously been suggested.