Evaluation of different preparations of aggregated human IgG for use as a standard in the assays of circulating immune complexes.

Comparative studies were carried out with regards to different preparations of aggregated human IgG (AGHG) to be used as the standard protein in the assays to estimate the amounts of circulating immune complexes. 5 different preparations of AGHG were used, in which WHO reference AGHG and glutaraldehyde-polymerized AGHG were included. These AGHG preparations were measured by the 4 different binding assays. Glutaraldehyde-polymerized AGHG, though weaker than heat-denatured AGHG in the binding activities, showed apparent dose-dependent curves in the 4 assays. It was also shown that molecular size of AGHG affect the binding activities: the smaller the molecular size, the weaker the binding activities. These results are considered to provide invaluable information for the standardization of the preparation of AGHG.