Interstrain variability of autoimmune encephalomyelitis in rats: multiple encephalitogenic myelin basic protein epitopes for DA rats.

We investigated T cell epitopes of guinea pig myelin basic protein (MBP) that induce experimental autoimmune encephalomyelitis (EAE) in DA rats, using synthetic peptides that correspond to regions of the guinea pig MBP molecule that are homologous to rat MBP. Four peptides were encephalitogenic when tested in DA rats. MBP63-81, which partially overlaps the dominant encephalitogenic MBP epitope for Lewis (LEW) rats, caused severe EAE in the DA strain but did not elicit EAE in LEW rats. MBP66-81 and MBP63-76 were also encephalitogenic for DA but not LEW rats. MBP79-99 also induced EAE in DA rats, although MBP87-99, the minor encephalitogenic LEW epitope, was inactive. This indicates that part of the 79-86 sequence is necessary for encephalitogenic activity in the DA strain. MBP101-120, and MBP142-167 were also encephalitogenic for DA rats. T cells from DA rats immunized with intact MBP proliferated in response to the whole protein and to MBP79-99, but were not stimulated to a significant extent by the other encephalitogenic peptides, suggesting that these may represent cryptic or subdominant epitopes. However, MBP63-81-specific T cell lines could be isolated by repeated restimulation with peptide, indicating that the peptide-specific T cells were present in DA rats at low frequency.