MULTIPLE CLASS-I MOTIFS REVEALED BY SEQUENCING NATURALLY PROCESSED PEPTIDES ELUTED FROM RAT T-CELL MHC MOLECULES

Class I major histocompatibility complex (MHC) molecules interact with a diverse array of self and foreign peptides. Displayed on the cell s urface, the class I/peptide complex provides an extracellular indicati on of the intracellular milieu. We have characterized the Lewis rat V beta 8.2+ T cell hybridoma C14/BW12-12A1 by FACS analysis and have use d immunoaffinity chromatography to purify class I molecules from these cells. Peptides eluted from the class I molecules have been fractiona ted by HPLC and sequenced. Self-peptide mixtures indicate two distinct peptide motifs, suggesting the possibility of multiple class I loci. The majority of the naturally processed peptide ligands were nonamers. Naturally processed peptide ligands fitting the first motif contained a hydrophobic leucine anchor residue at position three and a carboxyl -terminal serine anchor residue. A second motif was characterized by a tyrosine or phenylalanine residue at position three and a phenylalani ne or isoleucine carboxyl-terminal residue. Four peptides derived from the V beta 8.2 T cell receptor have sequences that fit these motifs, providing a mechanistic explanation for their immunoregulatory role. I dentification of these class I peptide binding motifs will be useful f or predicting potential CTL epitopes in studies on autoimmunity, immun oregulation and transplantation in the Lewis rat. (C) 1997 Wiley-Liss, Inc.