Fig. 3.

Intravital microscopy of human peripheral nerve. The challenges of visualizing leukocyte trafficking in endoneurial microvessels that form the blood-nerve barrier by intravital microscopy due to the multilayered organization of the human peripheral nerve are demonstrated in this illustration. Barriers that impede clear detection of leukocytes within these microvessels include axons and surrounding connective tissue within the endoneurium, the concentric and multilayered perineurium, and the longitudinally aligned collagen fibers and fat globules with the epineurium. The extrinsic vasa nervorum and epineurial macrovessels should be avoided as these blood vessels lack tight junctions and possess fenestrations