Exploitation of the Complement System by Oncogenic Kaposi's Sarcoma-Associated Herpesvirus for Cell Survival and Persistent Infection
Figure 5
Factor H is required for resistance to complement-mediated cytolysis of latently KSHV-infected endothelial cells.
(A–B) Most of latently KSHV-infected endothelial cells are resistant to complement-mediated cytolysis. TIME or TIME-KSHV cells were incubated with 10% normal human serum or heat-inactivated human serum for 1 h and 4 h, and the number of dead cells (A) and live cells (B) were determined. (C) Deposition of factor H but not factor I on TIME-KSHV cells following complement activation. TIME or TIME KSHV cells were incubated for 30 min with normal human serum, and stained for C5b-9 (green) and factor H (red in left panel) or factor I (red in right panel). Note the colocalization of factor H with C5b-9. The scale bar is 80 µm. (D) Factor H was required for resistance to complement-mediated cytolysis. TIME-KSHV cells were incubated for 1 h with heat-inactivated human serum, normal human serum, factor H-depleted human serum, factor H-depleted human serum reconstituted with purified factor H protein or factor I-depleted human serum, and the number of dead cells (left panel) and live cells (right panel) were determined. All the experiments were performed in 6 well plates with 6 repeats. Results are means ± SD from two to three independent experiments. * P<0.05 and ** P<0.01 by Student's t-test.