Fig. 3. Influence of heparin on the recruitment of vitronectin and invasion into host cells. (A) The dose-dependent influence of heparin on the binding of multimeric vitronectin to pneumococci was analyzed by flow cytometry using a polyclonal anti-vitronectin antibody and FITC-labelled secondary antibody. Results are presented as the mean ± s.d. of at least three independent experiments. (B) The influence of heparin on the adherence of pneumococci to Detroit 562 cells in the absence (none) or presence of 3.0 µg multimeric vitronectin (VN) was determined by immunofluorescence microscopy. Results are presented as the mean ± s.d. of at least three independent experiments. ^*P<0.01. (C) Dose-dependent inhibition by heparin of vitronectin-mediated pneumococcal invasion into Detroit 562 cells was measured by the antibiotic protection assay, and the number of internalized bacteria was determined after 4 hours. Results are presented as mean ± s.d. of at least three independent experiments.