Anticomplementary activity test for intravenous immunoglobulin preparation

Keeping the pH constant during the incubation of sample and complement solutions was an inportant factor to obtain a reproducibla ACA value. Lyophilized complement shows a pH of 8.8-9.0 after reconstitution. The pH of frozen complement is 7.2-7.4. When the ACA of an intravenous IgG (IVIG) was tested with the reconstituted complement, the ACA value was higher than when the preparation was tested with frozen complement.Ionic strength also affected the ACA test of an IVIG which did not contain ionic substances such as NaCl or glycine. Even when the pH and ionic strength of commercial IVIG preparations were standardized by dialysis, the concentration of IgG polymer did not necessarily correlate with the ACA value.