title: Chronological study of ultrastructural changes in the peripheral nerves in Marek's disease.
abstract: A chronological study was made of the ultrastructural changes in peripheral nerves following inoculation of 1-day-old chicks with a neurogenic strain of Marek Disease virus. No virus particles were found in nerves. Cellular infiltration of nerves was detected as early as 5 days after inoculation and by 3 weeks some nerves contained proliferative lesions which possessed many of the ultrastructural features characteristic of normal, reactive lymphoid tissue. About 4 weeks after inoculation, coinciding with the onset of neurological signs, areas of widespread demyelination appeared within these lesions; lymphocytes and macrophages penetrated and destroyed the myelin sheath, but spared Schwann cells and most axons. Later oedematous, sparsely infiltrated B type lesions were observed, some of which contained demyelinated nerve fibres undergoing repair; these were therefore a stage in the regression of the proliferative lesions. Our observations do not favour the hypothesis that cellular infiltration of nerves in Marek's disease is the direct result of auto-sensitization to normal myelin. They are consistent with the hypothesis that demyelination is a secondary feature and that the primary lesions are preferential sites for immune demyelination.
mesh_terms: D000818:Animals; D001917:Brachial Plexus / Q000648:ultrastructure; D002645:Chickens; D003711:Demyelinating Diseases / Q000209:etiology / Q000473:pathology; D008381:Herpesvirus 2, Gallid; D008221:Lymphoid Tissue / Q000648:ultrastructure; D008380:Marek Disease / Q000150:complications / Q000473:pathology*; D010525:Peripheral Nerves / Q000648:ultrastructure*; D012584:Sciatic Nerve / Q000648:ultrastructure; D013047:Specific Pathogen-Free Organisms; D014630:Vagus Nerve / Q000648:ultrastructure