Accelerated response to reinoculation in experimental allergic encephalomyelitis: histopathologic study.

Experimental allergic encephalomyelitis (EAE) was induced in Lewis rats by the injection of spinal cord tissue or myelin basic protein and adjuvants (Freund's or carbonyl iron or pertussis vaccine), or by adoptive immunization. After an interval of five to 12 weeks, the recovered rats were reinoculated by a different route and usually with a different adjuvant. The onset of the second attack was determined by the histologic detection of EAE lesions at intervals during the incubation period. In each of ten experiments, the second attack of EAE occurred one or two days earlier than in naive controls injected at the same time. Residual EAE lesions left over from the first attack could not explain the findings in the reinoculated rats. The accelerated response to the second inoculation may be related to the anamnestic response of classical immunology or to residual damage to the blood-brain barrier. Resistance to a second attack was not encountered in this histopathologic study.