Figure 3

IgM more efficiently induces complement activation than IgG1. MG1655-OmpX-StrepTagII was incubated with a concentration range of anti-StrepTagII IgM and IgG1 and 1.25% serum equivalent complement components. (a) C1q binding in the absence of other complement components, by incubating bacteria with antibody and C1-complex for 30 min. (b) C4b deposition in the absence of downstream complement components, by incubating bacteria with antibody and C1-complex for 15 min and adding C1-inhibitor and C4 for an additional 15 min. (c) C3b deposition with all CP complement components present as described in Fig. 1a. Samples were measured by flow cytometry and data represent mean ± SD of three independent experiments.