ORIGIN OF MACROPHAGES IN WALLERIAN DEGENERATION OF PERIPHERAL NERVES DEMONSTRATED AUTORADIOGRAPHICALLY

An attempt was made to ascertain whether the macrophages occurring in wallerian degeneration of peripheral nerves are of local or hematogenous origin. Normal adult mice were given closely repeated injections of 3H-thymidine to label leucocytes. At least 24 hours after the last injection one of the sciatic nerves was crushed. The other nerve served as control. At the moment of injury a differential count of white blood corpuscles showed, on the average, that 16% of the mononuclear cells and 42% of the polymorphonuclear leucocytes were labelled, compared with about 25-40% and 90%, respectively, on the second and fifth days after operation. Two to 11 days after the nerve injury, numerous labelled leucocytes were seen in and peripheral to the lesion, while only a slight difference in the density of labelled cells was observed in the central part of the nerve compared to the corresponding part of the control nerves. Some of the labelled cells closely resembled typical macrophages. The findings thus show that white blood corpuscles enter the degenerating parts of peripheral nerves in wallerian degeneration. Since such cells can transform into macrophages, part of the macrophage population in the degenerating nerves is presumably hematogenous. © 1969.