Experimental allergic neuritis. Ultrastructure of serum-induced myelin aberrations in peripheral nervous system cultures.

Mature myelinated cultures of mouse dorsal root ganglia (sometimes grown in combination with spinal cord tissue) have been exposed to unheated and heated (complement-inactivated) serum from rabbits with experimental allergic neuritis (EAN). Experimental cultures were examined for periods ranging from several hours to approximately 2 weeks of exposure. Some cultures were exposed to EAN serum for approximately 1 week then returned to normal medium for examination of the reversibility of the lesions. Unheated EAN serum induced demyelination of peripheral nervous system fibers within 96 hours of exposure. Following removal of the EAN serum, affected fibers remyelinated. Heated EAN serum produced a type of myelin swelling identical with that described previously in spinal cord explants exposed to serum from rabbits with experimental allergic encephalomyelitis. The lamellar spacing of the peripheral nervous system meylin was increased to approximately 23 nm. and the normal bifilar intraperiod line was increased to four leaflets. Some hypermyelination was seen. The swelling was incompletely reversible following removal of the heated serum. These findings are discussed in terms of their relevance to immunemediated demyelination and peripheral neuropathy associated with the hypergammaglobulinemic states.