MHC Class II-Bound Self Peptides from Autoimmune MRL <i>/lpr</i> Mice Reveal Potential T Cell Epitopes for Autoantibody Production in Murine Systemic Lupus Erythematosus

Abstract

The systemic lupus erythematosus-like syndrome in MRL/lpr mice involves high-titered IgG autoantibodies, particularly antinuclear Abs that target histones, DNA, and RNA particles. Although T cell help is required for the generation of antinuclear Abs, the epitopes recognized by such helper T cells are unknown. To address this question, we isolated and sequenced self peptides bound by MHC class II molecules from MRL/lpr mice. We identified a number of peptides that are not seen in similar preparations from nonautoimmune C3H animals. The "abnormal" peptide donors include histone, a protein component of a small nuclear ribonucleoprotein, ribosomal proteins, and RNA processing enzymes. We postulate that the peptides from these donors are T cell epitopes required for the generation of the most frequent antinuclear Abs specificities seen in MRL/lpr mice.