Effect of complement inhibitors on survival of serogroup B meningococci in plasma or whole blood from an unvaccinated adult subject. At time 0, ∼4750 CFU/mL N meningitidis serogroup B strain H44/76 were added to plasma or whole blood containing no complement inhibitor or inhibitors indicated. CFUs per milliliter were quantified in aliquots of blood or plasma collected at 1 and 3 hours postincubation. (A) Test conditions without adding anticapsular antibody. (B) Test conditions with adding 25 µg/mL of a meningococcal serogroup B anticapsular mAb (SEAM 12²⁷ ). Data are the mean CFU per milliliter (ranges) from replicate determinations. Δ Plasma, plasma heated for 30 minutes at 56°C to inactivate complement. The results were replicated in a second experiment with blood from the same donor. ACH-4471, factor D inhibitor of AP; ECZ, eculizumab.