Figure 4.

Relation of IgG anti‐αGal density and complement deposition on pig red blood cells (pRBCs). Complement deposition and antibody binding on pRBCs were measured by flow cytometry using detection antibodies against IgG (a and b), C4c (c), or C3c (d). (a) Antibody binding on pRBCs as a function of IgG anti‐αGal concentration are shown for different concentrations of hypogammaglobulinaemia human serum (HHS) as the complement source. (b) As in the previous panel (conducted in parallel) except that the experiments contained 10 mm EDTA. The data are expressed as the mean and standard deviation of two independent experiments. Curve fittings were performed in a third‐order polynomial model. (c and d) Complement deposition as a function of the level of bound IgG anti‐αGal for experiments performed with 1% HHS [antibody binding data from panel (b), blue curve]. Curve fitting was done in an exponential model ((c) P = 6·2 [95% CI 5·8–6·8), R ² = 1·0; (d) P = 5·6 (95% CI 5·2–6·2), R ² = 1·0].