MECHANISMS OF MACROPHAGE RECRUITMENT IN WALLERIAN DEGENERATION

Monocytes/macrophages are important effector cells in myelin removal d uring Wallerian degeneration. Experiments with the mouse mutant C57BL/ Ola revealed prolonged axonal survival and reduced phagocytic cell rec ruitment after nerve transsection. In the present study, we compared t he course of Wallerian degeneration in peripheral nerves of C57BL and C57BL/Ola mice in vivo and in vitro. In vivo experiments confirmed ear lier investigations describing a delayed degeneration in the C57BL/Ola mutant compared with C57BL mice which were used as control animals wi thout abnormal degeneration. Quite different results were seen in expe riments in vitro: degenerating nerve segments of C57BL/Ola mice reveal ed pronounced axonal breakdown even in the absence of non-resident pha gocytic cells. There was no difference in vitro compared with degenera ting nerves from C57BL mice. The differences observed between the in v ivo and in vitro situations suggest that axonal breakdown plays an imp ortant role in the initiation of macrophage recruitment to degeneratin g peripheral nerves.