Reactivity of normal T-cell lines to MBP isolated from normal and multiple sclerosis white matter

Abstract

T-cell reactivity to human myelin basic protein (MBP) has been extensively studied using T-cell lines and clones generated from both peripheral blood and cerebrospinal fluid, from normal controls and multiple sclerosis (MS) patients. These studies have largely utilized myelin basic protein isolated from control human adult white matter. In our study, we used MBP reactive T-cell lines as a probe to investigate antigenic differences in a series of MBP preparations isolated from either control human white matter or white matter from the central nervous system (CNS) of MS patients. Autologous peripheral blood derived mononuclear cells were used as antigen presenting cells (APC). Although the majority of T-cells were found to react equally well with all preparations of MBP isolated from both control and MS white matter, we were also able to identify T-cell lines which reacted well with all preparations of MBP isolated from controls but failed to react with MBP isolated from MS white matter. These differences were unlikely to reflect differences in degradation products or excess peptides present in the MS brain since SDS-PAGE and HPLC did not show any difference in the MS samples compared to the controls, and the concentration response curves for a human T-cell clone specific for the 84–102 region of MBP were similar for all the MBP preparations. We did not detect differences in amino acid content amongst MBP preparations although single amino acid substitutions cannot be ruled out. These results raise the possibility that MBP isolated from MS brain may differ in charge microheterogeneity which would affect antigenic determinants. The processing of MBP by different APCs is another variable which could underlie the differences in T-cell reactivity to various MBP preparations.