For total complement system activity, rabbit red blood cells and lamb plasma diluted to 5% in DGHB++ (100 μL of each) were mixed in a microtiter plate and incubated at 37°C for 1 h. Cells were removed by centrifugation(2,500 × g, 5 min, 4°C), and supernatant absorbance was measured at 405 nm (A405) using a micro-plate reader.