Fig 3.
Complement-opsonized O-antigen-deficient F. tularensis LVSs are internalized by asymmetric and often redundant tightly adherent pseudopod loops. The uptake of C7-deficient serum-opsonized parental LVS (A and B) and O-antigen-deficient LVSs (ΔwbtDEF [C, E, and G]; WbtIG191V [D and F]) by human monocyte-derived macrophages was examined by TEM. Whereas the parental LVS bacteria are engulfed within spacious, asymmetric pseudopod loops (A and B), the O-antigen-deficient mutants are internalized with more tightly adherent asymmetric loops (C and D) and within overlapping, onion-like arrays of adherent pseudopodia (E to G). (H) For comparison, uptake of E. coli by conventional phagocytosis is shown. The experiment was conducted three times with similar results. Bars, 1 μm.