Fig. 2.

Transmission electron micrographs (TEM) showing the ultra-structure of distinct TNT-like bridges in different cell types. (a) Open-ended TNT connecting two PC12 cells reconstructed from images of two consecutive 80 nm sections. The boxed areas are shown as higher magnification images (a₁, a₂). A continuous membrane is observed between the nanotube and the plasma membrane of the two connected cells. Modified from Rustom et al. (2004) Science 303:1007–1010. (b) Close-ended TNT-like bridge connecting two T cells and displaying a junctional border, reconstructed from images of 13 consecutive 60 nm sections. The boxed areas are shown as higher magnification images (b₁, b₂). The nanotube formed by one cell (b₂) protrudes into an invagination (arrowhead) of the connected cell (b₁). Modified from Sowinski et al. (2008) Nat Cell Biol 10:211–219. Scale bars, a, b, 1 μm; a₁, a₂, b₁, b₂, 500 nm