FIGURE 4.

Factor H promotes pneumococcal binding to PMNs via integrin CR3. Pneumococci were incubated with PMNs for 30 min, in the absence (control) or presence of anti-CD11b (2 μg), anti-CD18 (2 μg), or integrin CR3 (CD11b/CD18) ligand Pra1 (2 μg). Pneumococcal binding to PMNs was investigated in the absence (none) or presence of bacteria-bound Factor H by flow cytometry. The results were calculated (mean fluorescence intensity × percentage of gated positive events), and the data show the relative binding ratios compared with Factor H untreated pneumococci. *, p < 0.02.