Schwann cells responding to primary demyelination in vivo express p75NTR and c-erbB receptors: a light and electron immunohistochemical study.

We have used quantitative and qualitative light microscope immunohistochemistry to examine the expression of p75NTR and c-erbB receptors in Schwann cells in a demyelinating lesion induced by the intraneural injection of lysophosphatidyl choline (LPC). We report that levels of p75NTR, c-erbB2 and c-erbB4, as assessed using image analysis of immuno-peroxidase labelled sections, and c-erbB3, as assessed by eye, increased within each lesion site soon after the initiation of myelinolysis, peaked between 5 and 8 days after induction of demyelination and fell to undetectable levels at the onset of remyelination. Pre-embedding immunoelectron microscopy confirmed that Schwann cells ensheathing demyelinated axons were p75NTR positive. Immunolabel decorated overlapping processes of neighbouring Schwann cells, suggesting that in this context p75NTR could play a role in juxtacrine signalling between reacting cells. We conclude that upregulation of p75NTR and c-erbB receptors is a constitutive Schwann cell response to an acute disruption of the axon-Schwann cell relationship.