Specialised contacts of endoneurial fibroblasts with macrophages in wallerian degeneration.

Wallerian degeneration was induced by crushing the mouse phrenic nerve at the neck. During a chronological study, a specialised cell contact was often observed between the activated endoneurial fibroblast and the macrophage at the period when the removal of myelin debris by macrophages was prominent in the endoneurium. The specialised contact was characterised by paired subplasmalemmal linear condensations with a relatively constant thickness and varied length. It was sometimes asymmetrical. In these specialised cell membrane areas the intercellular space was filled with fine granular material showing a midline denser stratum. Coated vesicles were occasionally found in association with the subplasmalemmal densities. The specialised contacts with these features are quite different from any type of previously described cell contact between fibroblasts but are morphologically identical to those reported between cells of the mononuclear phagocytotic system. The significance of specialised contacts between the fibroblasts and macrophages in Wallerian degeneration is discussed.