RTX complement-dependent cytotoxicity (CDC) induced death of Daudi human cell line. A. Effect of varying concentration of normal human serum (NHS) with RTX 10 μg/ml (n = 3) as determined by propidium iodide staining. B. Effect of varying RTX concentration with 2% and 5% NHS (n = 3). Error bars represent mean standard error. C. Daudi cell death with 5% NHS represents CDC as evidenced by lack of cell death in complement free conditions (serum free media, C5 deficient serum, and heat inactivated (HI) serum).