Figure 2.

Complement is activated on the surface of Klebsiella pneumoniae and Staphylococcus aureus. ELISA plates were coated with mucoid or non-mucoid strains of K. pneumoniae or with S. aureus. Wells coated with zymosan were used as a control. Plates were incubated with NHS in BBS with Ca⁺² and Mg⁺² (A–C, E–G) or EGTA buffer (D, H). Complement C3b, C4b and C5b-9 deposition were detected using specific antibodies. C3b, C4b and C5b-9 deposition were observed on the surface of K. pneumoniae (A–C) and S. aureus (E–G) in conditions permissive for both the CP and the LP pathways. High levels of C3b via the AP were also detected on the surface of the bacteria (D, H). Results are means of duplicates ± SD.