Figure 2

Purified and serum C3 binding to S. aureus in varying glucose concentrations. (A, B) Purified C3 (10 μg/ml) binding to S. aureus in PBS increases at elevated levels of glucose. Data are mean ± SE for 4 independent experiments. (C) C3 binding to S. aureus incubated in 0.5% NHS in EDTA-GVBS^{- -} buffer, to prevent complement activation, increases at elevated glucose concentrations. Data are mean ± SE for 4 independent experiments. (D) Purified C3b binding to S. aureus in PBS increased at elevated levels of glucose. Purified C3b is incapable of activation. Data are mean ± SE for 4 independent experiments. (E) C3 bound to S. aureus incubated with purified C3 or 0.5% NHS in PBS was increased for 17 mmol/l glucose compared with 3 mmol/l. Purified standards for C3 [alpha (114 kDa) and beta (75 kDa) chain and iC3b products α2 ^' (42 kDa)] were included on the gel. (F) Purified C3 binding to S. aureus in PBS did not increase in 17 mmol/l (black bars) compared to 3 mmol/l (gray bars) for galactose, sucrose, or raffinose. Data are mean ± SE for 4 independent experiments. (G) Purified C3 binding to stationary phase (black circles) or log phase (grey squares) S. aureus in elevated glucose (17 mmol/l) increased over time. Data are mean ± SE for 3 independent experiments. (H) S. aureus bound by C3 in elevated glucose (17 mmol/l) and then incubated in 3 mmol/l glucose shows a rapid decrease for residual C3 bound to the bacteria. Data are mean ± SE for 3 independent experiments.