T-CELL AND B-CELL RESPONSES TO MYELIN BASIC-PROTEIN AND ENCEPHALITOGENIC EPITOPES

The major encephalitogenic epitope of myelin basic protein (MBP) for t he Lewis rat includes residues 68-84, although a minor epitope has bee n localized to MBP residues 87-99. We synthesized MBP68-84 and MBP87-9 9, and immunized rats with these peptides or with MBP in complete Freu nd's adjuvant (CFA). MBP and MBP68-84 induced paralytic experimental a utoimmune encephalomyelitis (EAE) at equimolar concentrations, whereas significantly higher dosages of MBP87-99 were required to elicit para lytic disease. Spleen cells (SpC) from MBP- or MBP68-84-immunized rats could be activated with either MBP or MBP68-84 to transfer EAE to rec ipients. Anti-MBP antibodies were detected by ELISA in rats immunized with MBP-CFA, and anti-MBP68-84 specific antibodies were present in se rum obtained from MBP68-84-immunized animals. However, these antibodie s were non-cross reactive. MBP87-99 elicited only a meager antibody re sponse to the immunizing peptide, and cross reactivity with MBP was no t observed. Thus, although MBP and each peptide exhibited encephalitog enic activity, and MBP and MBP68-84 were cross reactive at the T cell level, the absence of cross reactivity at the humoral level indicates that significant immunological differences exist between MBP and the s ynthetic determinants, which may reflect differences in epitope recogn ition by T and B lymphocytes.