Ultrastructural relations of macrophages to Schwann cells. An experimental study on regenerating peripheral nerves

The correlations between macrophages and Schwann cells are studied on transsectional sciatic nerves from rats using the electron microscope. As early as 1 day after operation typical macrophages can be found within the endoneurial space of the proximal stump. On the other hand, 1 and 3 days as well as 4 weeks after operation Schwann cells may show cytoplasmic features comparable to that of macrophages. Our findings suggest that (1) macrophages are not able to transform into Schwann cells and (2) Schwann cells can act as phagocytosing cells exhibiting characteristics of macrophages. But in this functional state they can only be diagnosed as Schwann cells if a basement membrane and/or included axons with mesaxons are present.