Flow cytometry–based complement dependent cytotoxicity assay.

Rituximab-induced CDC was measured by means of flow cytometry to evaluate PI uptake by tumor cells following 1-hour exposure to rituximab and human serum (source of complement). The PI⁺population, or those cells in which the membrane has become permeable by the complement cascade, is observed only following treatment with rituximab and human serum, as shown in this figure, with the use of Raji cells. In contrast, control cells treated with media alone, rituximab alone, and complement (human serum) alone show no PI uptake. Results from this assay correlate with standard chromium-release assays.