CDC induced by CD20 mAbs on B-cell lines.SU-DHL-4 (A), Daudi (B), or Raji (C) cells were incubated with a range of CD20 mAbs followed by addition of normal human serum (NHS, 20% vol/vol) as a source of complement and incubation at 37°C for 45 minutes. CDC activity was determined by PI exclusion assay as described in “Materials and methods.” The results show a representative experiment of 5 separate experiments. Symbols: rituximab, ▪; 7D8, ▴; 2F2, ▾ ; and 11B8, •.