Expression of NGF-receptors during immune-mediated and lysolecithin-induced demyelination of the peripheral nervous system.

Nerve growth factor receptor, expressed in Schwann cells during early development of the PNS, is rarely found in the normal mature PNS. Following nerve transection nerve growth factor receptor is re-expressed at high levels in the Schwann cells of the denervated nerve fibres. In this study we asked if demyelination caused by an immune-mediated process or by physical destruction of myelin is associated with expression of nerve growth factor receptor, and if so, what cells are positive. We examined spinal roots and sciatic nerves from rats with experimental autoimmune neuritis and sciatic nerves from rats with focal demyelination produced by local application of lysolecithin. Both in 1 micron serial cryosections and in immunostained teased nerve fibres we found that the Schwann cells that were associated with demyelinated internodes expressed nerve growth factor receptor. Immunoreactivity for nerve growth factor receptor appeared first in a perinuclear ring, probably corresponding to the Golgi complex. In completely demyelinated internodes the postmitotic Schwann cells ensheathing the axons expressed nerve growth factor receptor on their plasmalemma. Neighbouring Schwann cells with intact myelin sheaths remained nerve growth factor receptor negative. In contrast, Schwann cells of neighbouring unmyelinated fibres expressed prominent nerve growth factor receptor immunoreactivity. These data further indicate that expression of nerve growth factor receptor by Schwann cells does not require axonal degeneration, but can be stimulated by some factor associated with acute demyelination.