Identification and characterization of a T cell-inducing epitope of bovine ribonuclease that can be restricted by multiple class II molecules.
An immunodominant epitope of bovine RNase restricted by I-Ek molecules was identified using a T cell hybridoma recognizing RNase. This epitope was localized to the peptide RNase(90-105). Single conservative amino acid substitutions were made at each of the positions 94 through 105. It was found that only at one position, Asn-103, were conservative substitutions not allowed. This residue was shown to be the critical residue in determining T cell specificity. The ability of RNase(90-105) and the well-defined T cell epitope, HEL(46-61) to stimulate mouse strains expressing different independent H-2 haplotypes was examined using a T cell proliferation assay. The response to HEL(46-61) was completely restricted to mice expressing an I-Ak molecule. In striking contrast, 6 of 10 different mouse strains, H-2b,f,k,q,s,u, mounted vigorous T cell responses to RNase(90-105). The response was restricted to both I-A and I-E molecules, including I-Ab, I-Af, I-Ek, I-Aq, and I-As. H-2d mice were nonresponders to RNase(90-105), which was shown to be due to the failure of RNase(90-105) to bind to I-Ad molecules. A variant RNase(90-105) peptide was generated, containing an I-Ad binding motif, that could bind to I-Ad molecules. Despite its ability to bind, this variant peptide was not able to stimulate a response in H-2d mice. This result demonstrates that the ability of a peptide to bind to an Ia molecule is necessary but not always sufficient for a response to occur. Thus, in contrast to the highly restricted HEL(46-61) determinant, the RNase(90-105) determinant is permissive in its binding to Ia molecules. These results show that in the universe of T cell inducing epitopes contains both highly restricted and broadly restricted epitopes are found.
Chen
J S
JS
Department of Pathology, Washington University School of Medicine, St. Louis, MO 63110.
Lorenz
R G
RG
Goldberg
J
J
Allen
P M
PM
D000595:Amino Acid Sequence; D000818:Animals; D000938:Antigen-Presenting Cells / Q000276:immunology; D002417:Cattle; D000939:Epitopes; D000949:Histocompatibility Antigens Class II / Q000276:immunology*; D008213:Lymphocyte Activation; D051379:Mice; D008815:Mice, Inbred Strains; D008969:Molecular Sequence Data; D012260:Ribonucleases / Q000276:immunology*; D013329:Structure-Activity Relationship; D013601:T-Lymphocytes / Q000276:immunology*
D000939:Epitopes; D000949:Histocompatibility Antigens Class II; C024138:I-E-antigen; D012260:Ribonucleases