Relapsing experimental allergic encephalomyelitis induced with isolated myelin and with myelin basic protein plus myelin lipids.

To test the ability of different spinal cord fractions to reproduce the clinicopathological features of relapsing experimental allergic encephalomyelitis (R-EAE), groups of young guinea pigs were inoculated with: (1) spinal cord myelin; (2) delipidated myelin; (3) reconstituted myelin and (4) MBP plus myelin lipids. The four sets of antigens induced acute EAE in most of the animals tested. During an observation period of 18 months, only one clinical relapse was observed in animals sensitized with myelin and with MBP plus myelin lipids. Extensive CNS demyelination was found in relapsing animals injected with myelin. No demyelinated lesions were observed in non-relapsing animals. By contrast, half of the surviving guinea pigs injected with MBP plus myelin lipids had demyelinated lesions, irrespective of whether they relapsed or not. The inability of the spinal cord myelin fractions to fully reproduce the R-EAE model suggest that other non-myelin antigens may be involved in the pathogenesis of multiple relapses.