Normal bactericidal capacity against Neisseria meningitidis in serum from a patient with a hemolytically inactive complement factor 8 (C8).

The bactericidal capacity of serum against Neisseria meningitidis from a 27-year-old male with two episodes of meningococcal meningitis and C8 deficiency was compared to that of normal human serum (NHS) without demonstrable antibodies against Neisseria. The in vitro bactericidal capacity of the patient serum was found to be equal to that of NHS. Incubation of both sera at 56 degrees C for 30 minutes abolished the bactericidal effect. Rocket-immunoelectrophoresis analysis of molecules immunochemically identifiable as C8 revealed no consumption of these molecules in any of the sera in the bactericidal assay. No hemolytic complement activity was found in the patient serum, whereas the donor serum had normal total hemolytic complement activity with significant consumption of C8.