Prevention of experimental allergic encephalitis in guinea-pigs with spinal cord protein: optimum pretreatment schedules and appraisal of plausible mechanisms.

Pretreatment of Hartley guinea-pigs with three injections of 100 microgram of the purified bovine spinal cord protein, (SCP), protected tham from clinical experimental allergic encephalitis (EAE) when they were subsequently challenged with 50 microgram of purified bovine myelin basic protein (MyBP) in Freund's complete adjuvant (FCA). The length of the optimum pretreated schedule was found to be 1 week and the animals were fully protected for 2 weeks. Protection declined thereafter so that by 4 weeks following pretreatment only 40% of the animals were protected. The protected state could be restored several weeks after it had lapsed by repeating the treatment with SCP. Immature animals did not respond well to pretreatment with SCP. Evidence was presented to indicate that specific, non-specific immune suppression or anti-SCP IgG were not involved to a significant extent in protection. SCP-treated guinea-pigs regularly displayed delayed skin hypersensitivity to MyBP after sensitization but there was no correlation between the degree of cutaneous reactivity and protection from disease. Because SCP is localized in the nerve axon, the speculation was advanced that anti-SCP blocking factors might be responsible for preserving axonal function in SCP-treated animals sensitized with MyBP.