Beneficial effect of orally administered myelin basic protein in EAE-susceptible Lewis rats in a model of acute CNS degeneration.

Axonal injury in the central nervous system (CNS) results in the degeneration of directly damaged fibers and also in the secondary degeneration of fibers that escaped the primary insult. Studies have shown that a protective T cell-mediated autoimmunity directed against myelin-related self-antigens is a physiological response to CNS insult, spontaneously elicited in strains that are constitutionally resistant to experimental autoimmune encephalomyelitis (EAE) but not in EAE-susceptible strains. The protective response following axonal injury can be induced in susceptible rats and boosted in resistant rats by passive or active immunization with myelin-related antigens. Here we show that oral administration of low-dose myelin basic protein (MBP) over a 5-day period is beneficial for post-traumatic survival of neurons in Lewis (EAE-susceptible) rats. Protection was accompanied by increased expression of the costimulatory molecule B7.2 in the traumatized nerves, similar to that seen after passive transfer of MBP-specific T cells. These results support the contention that properly controlled autoimmunity is the body's defense mechanism against non-infective insults. Oral immunization with MBP can be viewed as a way to control the autoimmunity capable of fighting off the consequences of CNS injury in EAE-susceptible strains.