GL-2045 protects Ab-opsonized cells from CDC. Ab-opsonized SUDHL4, Ramos, and SRBCs were incubated with either 6% (A-B), 1.5% (C), or 50% (D-F) NHS pretreated with GL-2045, HAGG, or IVIG at indicated concentrations. Cell apoptosis/death was measured by Annexin V/7-AAD staining and analyzed by FACS. SRBC hemolysis was evaluated spectrophotometrically. The results are shown as the least squares mean ± SE estimated by ANCOVA. Natural log variance stabilizing transformation and Tukey procedure for multiple comparisons adjustment were used to test the differences. *P < .05, **P < .01, ***P < .001 compared with no-treatment control.