Myasthenia gravis (MG) and experimental autoimmune MG (EAMG) are T cell-dependent, antibody-mediated
autoimmune diseases. A
dual altered peptide ligand (APL) that is composed of the tandemly arranged two single
amino acid analogues of two myasthenogenic
peptides, p195-212 and p259-271, was demonstrated to down-regulate in vitro and in vivo MG-associated autoreactive responses. The aims of this study were to investigate the possible role of Fas-FasL-mediated apoptosis in the down-regulatory mechanism of the
dual APL. We demonstrate here the effect of the
dual APL on expression of key molecules involved in the Fas-FasL pathway, in a p195-212-specific T cell line, in mice immunized with Torpedo
acetylcholine receptor and in mice afflicted with EAMG (induced with the latter). In vitro and in vivo results show that the
dual APL up-regulated expression of Fas and FasL on the CD4 cells. Expression of the pro-apoptotic molecules,
caspase 8 and
caspase 3, was significantly up-regulated, while anti-apoptotic cFLIP and Bcl-2 were down-regulated upon treatment with the
dual APL. The
dual APL also increased phosphorylation of the
mitogen-activated protein kinases, c-Jun-NH2-terminal
kinase and p-38, known to play a role in the regulation of FasL expression. Further, in the T cell line incubated with the
dual APL as well as in mice of the SJL inbred strain immunized with the myasthenogenic
peptide and treated concomitantly with the
dual APL, the percentage of apoptotic cells increased. Results strongly indicate that up-regulation of apoptosis via the Fas-FasL pathway is one of the mechanisms by which the
dual APL reverses EAMG manifestations in C57BL/6 mice.