Analysis of MCP binding to C3b and C4b. C3b and C4b binding assays were performed at 25 mM (Figure S1) and 50 mM (shown here) salt concentration. CHO cell lysates (5 × 106 to 25 × 106 MCP molecules as measured by ELISA) of R69W, A304V, and wild type from both transient transfections and stable cell lines were used. Data represent means (± SD) for 4 experiments at 50 mM.