Figure 4.

Inhibiting effect of human plasma on neutrophil lysis and subsequent platelet activation by PVL correlates with the amount of antibodies against PVL in the plasma/serum. Human neutrophils were incubated with 2.5% human plasma obtained from 18 different blood donors, or with 2.5% human serum (HS), human serum IgG depleted (HS IgG depl.) or human serum anti-PVL antibody depleted (HS depl.). Cell damage after incubation with PVL (5 nmol/L) was measured by flow cytometry assessment of propidium-iodide staining. Antibodies against PVL in the plasma/ serum were measured by ELISA (a). Data show mean ± SD from 3 different experiments. Pearson’s correlation coefficient was used to determine the relationship of percentage of undamaged neutrophils and anti-PVL-antibody titre. Inhibiting effect of plasma/serum from donors with a high titre of anti-PVL antibodies on platelet fibrinogen-binding in the presence of isolated human neutrophils: PVL (25 nmol/L)-induced binding of fibrinogen-FITC to gel-filtered platelets in the presence of isolated human PMNLs (10,000 per µL) and 10% plasma/serum from donors with high (donors C and D) or low anti-PVL titers (donors A and B) was measured by flow cytometry and compared to the control without plasma (100%). (b) Data show mean ± SD from 3 different experiments, one-way ANOVA followed by Bonferroni testing (*p < 0.05; **p < 0.01).