Figure 2.

Anti-dsDNA antibodies bind to annexin II on the surface of HMC. (A) Plasma membrane proteins from HMC were subjected to Western blot and probed with control IgG (lane 1) and three different human anti-dsDNA antibodies (lanes 2 through 4). Three bands (H1, H2, and H3) showed binding with anti-dsDNA antibodies but not control IgG. (B) MALDI-TOF spectra obtained from proteins H2 (upper panel) and H3 (lower panel) after trypsin digestion and tryptic peptide sequencing show that both proteins contain annexin II with a minor quantity of annexin V in H3. (C) Plasma membrane proteins were immunoprecipitated with either monoclonal anti-annexin II (upper panel) or polyclonal goat anti-annexin V antibodies (lower panel), subjected to Western blotting, and then probed with control human IgG or three different anti-dsDNA antibodies. The results demonstrated a high reactivity of anti-dsDNA antibodies to annexin II. (D) DNA-free human recombinant annexin II was subjected to Western blot analysis and probed with control IgG (lane 1), control IgG preincubated with recombinant annexin II (lane 2), anti-dsDNA antibody (lane 3), or anti-dsDNA antibody preincubated with human recombinant annexin II (lane 4). One representative blot is shown.