Figure 3.

SIC inhibits the binding of C5b-7 complexes to cell membranes. Reactive lysis of guinea pig erythrocytes was initiated by addition of pre-formed C56 complex followed by either (a) 1/40 normal human serum in 10 mm EDTA, or (b) purified C7, C8 and C9. Cells preincubated with SIC were protected against lysis compared to control cells incubated with BSA. When added to cells after C5b-7 sites had been formed on their surfaces (c), SIC had very little effect upon haemolysis, showing that it works by blocking uptake of C5b-7 complexes. A comparison of the activity of SIC and clusterin (d) showed that SIC and clusterin were equally efficient at inhibiting haemolysis of GPE by C56 and 1/40 NHS/EDTA. Data are expressed as mean ± SEM of triplicate results from a typical experiment. Error bars are too small to be seen on some data points.