The case against epitope spread in experimental allergic encephalomyelitis

Area of Science:

• Neuroimmunology
• Autoimmunity
• T-cell immunology

Background:

• Epitope spread is a proposed mechanism for autoimmune T-cell response diversification.
• It may explain the cyclical nature of autoimmune demyelination, including attack, quiescence, and reactivation.
• Previous studies lacked strong correlation between epitope spread, disease severity, and relapse.

Purpose of the Study:

• To investigate determinant spread during relapsing experimental allergic encephalomyelitis (EAE) in SJL mice.
• To correlate epitope recognition and cytokine production with disease severity and relapse.
• To evaluate the role of epitope spread in the cyclical nature of autoimmune demyelination.

Main Methods:

• Conducted a systematic, longitudinal study in SJL mice with relapsing-remitting EAE.
• Analyzed T cells from spleen, lymph node, and central nervous system (CNS).
• Assessed epitope recognition, cytokine production (IFN-gamma), and proliferative responses.

Main Results:

• Little to no determinant spread was observed in T cells from spleen, lymph node, or CNS.
• The strongest correlate of relapse was the reappearance of CNS-infiltrating T cells responding to the original epitope.
• This response involved strong proliferation and interferon-gamma production.

Conclusions:

• Data do not support a general role for determinant spread in EAE relapse.
• A focused T-cell response to the initial disease-inducing epitope is crucial for relapse.
• Reactivation involves a strong proliferative and IFN-gamma response to the original epitope, not spread to new epitopes.