Fig. 3

Assessment of the potential toxicity risks of IgG1 and IgG4 Fc hexamers. a Human whole blood vs PBMC cytokine release by Fc hexamers. Whole blood or PBMC from the same donors was cultured for 24 h with a titration of IgG1 Fc hexamer (L309C) or positive controls alemtuzumab (100 μg/ml) and IVIG (2232 μg/ml). Data represent mean ± SEM of plasma IFN-γ concentration, n = 3 donors. b Comparison of IgG1 and IgG4 Fc hexamers (L309) in whole-blood cytokine release. Blood was cultured for 24 h with a titration of Fc hexamers or controls. Data represent mean ± SEM of plasma IFN-γ concentration, n = 3 donors. c Depletion of neutrophils from whole blood reduces cytokine release. Whole blood (WB) or neutrophil-depleted (ND) blood was stimulated with a titration of IgG1 Fc hexamer or controls for 24 h. Data represent mean ± SEM of plasma IFN-γ concentration, n = 3 donors. d Comparison of IgG1 and IgG4 Fc hexamers in platelet activation. Human whole blood was incubated with a titration of Fc hexamers (L309) or positive controls (TRAP/PMA) at room temperature for 25 min. Data represent the mean ± SEM of % of platelets CD62p⁺, n = 3 donors. e Comparison of IgG1 and IgG4 Fc hexamers (L309) in C1q binding. Relative ability of Fc hexamers to bind C1q was measured by ELISA. Data represent mean ± SD of duplicate tests