Fig. 6: Stevioside reduced capsule-mediated protection against the complement system.
From: Stevioside curbs Streptococcus pneumoniae infection via inhibiting capsule biosynthesis
A Immunofluorescence microscopy analysis of C3b/iC3b deposition on the surface of S. pneumoniae D39 exposing to 20% NHS in the presence of DMSO or indicated concentrations of stevioside for 3 h. Cells were then rinsed and stained with APC-conjugated anti-C3b/iC3b antibody. A serum-free group served as a negative control to exclude the non-specific antibody binding. Scale bars, 10 µm. B The positive ratio of C3b/iC3b-stained bacterial cells was quantified by ImageJ. (n = 3). C Immunofluorescence microscopy analysis of C5b-9 complex formation on the surface of S. pneumoniae D39 exposed to 20% NHS in the presence of DMSO or indicated concentrations of stevioside for 3 hours. Bacterial were then rinsed and stained with a mouse anti-C5b-9 antibody and Alexa Fluor 488-conjugated goat anti-mouse IgG. Scale bars, 10 µm. D The ratio of C5b-9-positive bacterial cells was quantified by ImageJ. (n = 3). All data from three biological replicates were presented as mean ± SD and analyzed using unpaired two-tailed Student’s t-test. *P < 0.05, and ns, no significance compared with the DMSO vehicle group.
