Serum opsonins to serogroup B meningococci in meningococcal disease

The opsonic activity to serogroup B meningococci (B:15:P1.16) was measured in sera from 101 patients with meningococcal disease using a chemiluminescence method. On admission to hospital the opsonic activity was lower in 12 patients who died than in survivors (p = 0.0007). A close association was observed between the opsonic activity and the duration of symptoms before admission, the severity of the disease, and the levels of IgG antibodies to the outer membrane complex (15:P1.16). The opsonic activity was low in 2 premorbid sera compared to healthy controls. The mean opsonic activity peaked 2 weeks after admission and was still high 3-5 years later. Meningococcal strains of different serogroups, serotypes and subtypes induced a similar increase in opsonic activity to B:15:P1.16 meningococci. No increase in activity was observed in sera from patients with meningitis and septicemia caused by other bacteria. Serum opsonins seem to be of significant importance in the host defence against serogroup B meningococci.