CD55, but not CD46, inhibits complement-mediated lysis.

The indicated cells were incubated in presence (+) or absence (−) of rituximab and 25% NHS and 10 μg/mL anti-CD55, -CD46, or -CD19 (all IgG1). Cell death was measured after 1 hour at 37°C by cell count. The results are representative of at least 5 separate experiments. The statistical significance is shown by asterisks. *P < .05; ** P < .01; ***P < .001 (Student t test). ND, not determined.