Membrane-bound C7 is anchored to vimentin on the cell surface. (A) FACS analysis of nonpermeabilized HUVECs for surface expression of vimentin using mAb anti-vimentin (black line) or unrelated IgG (gray line) (10 μg/ml) followed by RPE-labeled secondary antibody. (B) Western blot of C7 affinity-purified from cell lysate analyzed with polyclonal anti-C7 (1:1000) (track 1) or anti-vimentin (1:100) (track 2) followed by AP-conjugated anti–goat antibodies. (C) ECs were incubated with goat IgG to C7, or with goat IgG to C3 or C6, as controls, and then lysed. The expression of C7/vimentin complex in the cell lysate was documented by AC-ELISA using protein G–coated wells to trap the complex containing antibodies to the C components in the cell lysate and goat IgG anti-vimentin to reveal the presence of this protein in the complex. The results are expressed as mean (± SD) of triplicate determinations of 3 separate experiments. *P < .01 versus controls.