Myelin phagocytosis in Wallerian degeneration. Properties of millipore diffusion chambers and immunohistochemical identification of cell populations.

Myelin phagocytosis in Wallerian degeneration was studied using a model of murine sciatic nerve degeneration in millipore diffusion chambers in the peritoneal cavity of host mice. Immunocytological investigations showed the dependence of myelin digestion on the invasion of Fc-positive, Mac-1-positive and partly Ia-positive monocytes. Lymphocytes did not play a prominent role. Compared to Wallerian degeneration in situ, phagocytosis was decreased in nerves enclosed by millipore membranes on both sides of the chamber. The membrane acted as a trap for invading monocytes/macrophages. Neither tissue integrity nor genetic strain influenced the degree of phagocytosis. A modification of the experimental technique is introduced which permits myelin phagocytosis in the peritoneal cavity in a degree comparable to that in Wallerian degeneration in situ.