FIG. 4.

Electron micrographs showing the uptake of various spirochetes by human monocytes. Human monocytes (2 × 10⁶) were incubated with various spirochetes (2 × 10⁷; arrows) for 45 min. Pseudopod coils are shown for B. afzelii (A; bar = 0.1 μm), T. phagedenis (B; bar = 0.4 μm), L. interrogans SV icterohaemorrhagiae Bücker (C; bar = 0.5 μm), and B. parkeri (D; bar = 0.5 μm); in panels A, C, and D, the pseudopod coils are partly covered by contrarotating surplus pseudopods (arrowheads). In panel E, a pseudopod coil enwrapping an L. interrogans SV pomona organism has already been transformed to an organelle exclusion zone (asterisk) within the cytoplasm of the monocyte. The remnants of the fused pseudopod membranes are clearly visible (bar = 2.0 μm). The pseudopod whorls are easily distinguished from the funnel-like, symmetrical surface extensions of conventional phagocytosis, shown in panel F for a B. burgdorferi sensu stricto organism (bar = 0.2 μm). The asterisk in panel D indicates a spacious phagosome.