Estimation of Functional Activity of Ionized Calcium for Complement System Reactivity Assessment

We proposed a new indicator for evaluation of functional activity of Ca(2+) in human blood serum based on lysis of sheep erythrocytes with 10% human blood serum in the presence of 0.55 mM ethylene glycol tetraacetic acid at 37°C for 10 min. After incubation, the degree of sheep erythrocytes lysis inhibition is estimated: inhibition of complement hemolytic activity <30% is considered as high functional Са(2+) activity, inhibition by 31-70% corresponds to normal activity, and >71% indicates low activity. The comparative studies of complement activating function of heterophilic antibodies, complement system reactivity in the presence of 0.29 M NaCl, and functional activity of ionized Ca(2+) make possible estimation of the individual's immune status.