Fig. 4

PrtA immunization facilitated opsonophagocytosis. a FITC-labeled S. pneumoniae D39 cells were incubated with pooled antisera (n = 4) from PrtA1/curdlan- or curdlan-immunized groups. The opsonized bacterial cells were identified using Dylight™ 649-anti-mouse IgG antibody and were visualized using immunofluorescence microscopy (DeltaVision Elite) under 40× oil objective. The images were processed by deconvolution. b FITC-labeled D39 cells were mixed with serially diluted antisera and were incubated with PMA-activated murine macrophage RAW264.7. The proportion of RAW264.7 cells to internalized bacterial cells was examined using flow cytometry after extracellular fluorescence quenching with trypan blue. The sera were pooled from four mice in each group, and the results were a representative of two independent experiments