FIGURE 6.

Factor H-mediated pneumococcal internalization by epithelial cells is inhibited by the integrin-binding protein Pra1. A, pneumococcal adherence to A549 cells was determined in the absence (control) or presence of integrin CR3 ligand Pra1 (2 μg ml⁻¹). The infection assays were conducted with or without (none) pretreatment of pneumococci with Factor H. *, p < 0.03; ns, not significant, relative to infections conducted in the absence of Factor H. B, immunofluorescence microscopy of pneumococcal adherence via Factor H to A549 cells in the absence (control) or presence of Pra1. C, invasion and intracellular survival of pneumococci in A549 cells were monitored in the absence (control) or the presence of Pra1 (2 μg ml⁻¹) by the antibiotic protection assay. The results are shown relative to infections conducted in the absence of Pra1 and Factor H. *, p < 0.02.