Figure 7. Annexin A2 increases complement activation on the surface of tubular epithelial cells and endothelial cells.

A) Murine tubular epithelial cells were incubated with normal mouse serum, and recombinant annexin A2 (inset) was added to the reaction. C3b deposition on the cells was measured by flow cytometry. The addition of annexin A2 increased C3b deposition on the cells (n = 6). B) Viable and necrotic cell populations were identified using propidium iodide, and C3b deposition on these populations was examined by flow cytometry. More C3b was detected on the surface of necrotic cells than viable cells. The addition of annexin A2 increased C3b deposition on both the viable and the necrotic cell populations. C) We also tested whether annexin A2 affects complement activation on endothelial cells. There was a trend towards greater C3b deposition when the cells were exposed to serum in the presence of annexin A2 (n = 3). *P < 0.05, **P<0.01, ***P< 0.001.