Figure 8.

Phagocytosis in whole blood is impeded by inhibition of complement and enhanced by pCRP-opsonization as measured by confocal fluorescence microscopy. Blood was treated as described above. 15 min before the exposure to the phagocytosis targets, the relevant inhibitor was added, and phagocytosis was assessed at 20x magnification. Shown are representative results for pCRP-opsonized S. pneumoniae, Compstatin inhibited cells, and the untreated control group, respectively. Compstatin-treated phagocytic leukocytes (DAPI, blue) showed significantly reduced activity in the phagocytosis of S. pneumoniae-FITC targets (green). When pCRP was added to the targets first, the number of phagocytized particles was significant higher. Scale bar indicates 50 µm (A). However, mCRP added to the targets showed no difference to the unstimulated control. Results are presented as means and S.E.M. and P values were calculated with ANOVA and Tukey post hoc test, n = 6, ns, not significant, ** P < 0.01, *** and **** < 0.001, and < 0.0001 (B). Only FITC-positive targets (green) in direct proximity to the nucleus (blue) and surrounded by F-actin (white) were assumed to be phagocyted particles. Scale bar indicates 20 µm (C).