Inflammation and proinflammatory cytokine production,but no demyelination of facial nerves,in experimental autoimmune neuritis in Lewis rats

Experimental autoimmune neuritis (EAN) is a CD4⁺ T cell-mediated, inflammatory demyelinating disease of the peripheral nervous system (PNS) that serves as a model for Guillain–Barré syndrome (GBS) in humans. The facial nerve paralysis is relatively commonly found in GBS patients. Here, EAN was established in Lewis rats by immunization with P2 peptide 57–81, a purified component of peripheral nerve myelin, and Freund's complete adjuvant (FCA). To study whether the facial nerves are involved in the pathogenic process during the EAN course, we observed the clinical and pathological changes as well as cytokine production in facial nerves on Day 14 postimmunization (p.i.), i.e. at height of clinical EAN. As a result, all rats immunized with P2 peptide 57–81 developed severe EAN on Day 14 p.i., but none of the rats manifested clinical signs of facial nerve paralysis. Additionally, only mild inflammatory cell infiltration and proinflammatory cytokine, interferon-γ (IFN-γ) and tumour necrosis factor (TNF-) production as well as devoid demyelination were seen in facial nerves of the EAN rats. On the contrary, severe inflammation and demyelination as well as upregulated IFN-γ and TNF- production were observed in sciatic nerves of the same EAN rats. The underlying mechanism for the difference of the local manifestation of the disease process of EAN remains to be resolved.