EndoS inhibits hemolysis and agglutination of sensitized RBCs and prevents binding of C1q to sensitized RBCs. (A) Relative amount of hemoglobin quantified by 2,7-diaminofluorene in plasma after incubation of human blood with antiserum against human RBCs, pretreated with EndoS or not. (1)Direct addition of EndoS to blood containing RBC antiserum. (2)EndoS alone added to blood. NS indicates not significant. (B) Blood smears. (Top panel) A total of 80 μg of anti-RBC IgG added to 700 μL human blood, diluted 35 times in PBS, and incubated 1 hour at 37°C. (Middle panel) Anti-RBC treated with EndoS before addition to blood. (Bottom panel) No addition of antibodies. (C) Relative C1q deposition onto IgG-sensitized RBCs detected using FITC-conjugated anti–human C1q.
