Elevated opsonic activity for Porphyromonas (Bacteroides) gingivalis in serum from patients with a history of destructive periodontal disease. A case: control study.

We have measured the opsonic capacity of serum for the phagocytosis of Porphyromonas (Bacteroides) gingivalis by polymorphonuclear leucocytes (PMN) in 35 patients with a history of destructive periodontitis and 35 matched control subjects. The serum from cases, tested at concentrations of 8% and 0.8% opsonised P. gingivalis for phagocytosis by PMN to a level significantly greater than controls (p < 0.0001 and < 0.01 respectively). IgG antibody levels to P. gingivalis whole cells estimated by ELISA were also significantly higher in the cases (p < 0.0001). The IgG antibody levels correlated significantly with the opsonic capacity of the serum tested at 8% concentration in controls (r = 0.371, p = 0.03) but not in cases (r = 0.235, p = 0.17); in 0.8% serum, the opsonic capacity of the cases and controls were not significantly correlated. Elevated opsonisation by serum was a significant predictor that a subject was a case rather than a control, even after allowing for the effect of elevated IgG antibody in the cases. The data suggest that an elevated capacity of serum to opsonise P. gingivalis is a distinctive feature in patients with past destructive periodontal disease.