Abstract
Pathogenic antigens involved in the induction of Heymann nephritis (HN), an experimental rat model of human membranous nephritis, have been identified in megalin (gp330) and the receptor-associated protein (RAP) [1,2]. A pathogenic epitope has been identified in RAP (amino acid 1-86) that plays a significant role in the formation of immune deposits in glomeruli in HN. A synthetic peptide (P31-53) derived from RAP1-86 contains a pathogenic epitope recognized by antibodies eluted from glomerular immune deposits and includes two putative RT-1B1 MHC class II-binding motifs. We have investigated whether RAP P31-53 can be recognized by T cells. Five peptide-specific T cell lines were generated from regional lymph node (LN) T cells from Lewis rats immunized with P31-53. The T cell lines were characterized by using a T cell proliferation assay for their specificity, FACS and MHC restriction assay for the phenotype, reverse transcription-polymerase chain reaction for TCR Vbeta repertoire and cytokine expression, and cloning and sequencing for the analysis of the CDR3 sequence of TCR. The helper function of the T cell line was confirmed by autoantibody production in vitro. In this study, we clearly identify that the synthetic pathogenic peptide P31-53 contains a T cell epitope recognized by CD4+ Th2 cells in Lewis rats. This recognition was restricted by MHC class II RT1.B1. These CD4+ Th2 cells were able to promote B cells to produce specific antibodies and used a restricted set of TCR Vbeta genes with preferential usage of Vbeta18. A charged amino acid motif at the CDR3 region of predominant TCR Vbeta subfamilies may contribute to the specific ability of these cells to recognize the immunogenic T cell epitope within RAP peptide P31-53.