Unresponsiveness to a self-peptide of mouse lysozyme owing to hindrance of T cell receptor-major histocompatibility complex/peptide interaction caused by flanking epitopic residues.
A self-peptide containing amino acid residues 46-61 (NRGDQSTDYGIFQINSR) of mouse lysozyme (ML) (p46-61, which binds strongly to the A(k) molecule but does not bind to the E(k) molecule), can induce a strong proliferative T cell response in CBA/J mice (A[k], E[k]) but no response at all in B10.A(4R) and CBA/J mice. The critical residues within p46-59 are immunogenic in both B10.A(4R) and CBA/J mice. The critical residues within p46-61 reside between amino acid positions 51 and 59. T cells of B10.A(4R) mice primed with the truncated peptides in vivo cannot be restimulated by p46-61 in vitro. This suggests that T cell receptor (TCR) contact (epitopic) residue(s) flanking the minimal 51-59 determinant within p46-61 hinder the interaction of the p46-61/A(k) complex with the appropriate TCR(S), thereby causing a lack of proliferative T cell response in this mouse strain. Unlike B10.A(4R) mice, [B10.A(4R) x CBA/J]F1 mice responded vigorously to p46-61, suggesting that thymic APC of B10.A(4R) mice do not present a self ligand to T cells resulting in a p46-61-specific hole in the T cell repertoire in B10.A(4R) or the F1 mice. Moreover, APC from B10.A(4R) mice are capable of efficiently presenting p46-61 to peptide-specific T cell lines from CBA/J mice. The proliferative unresponsiveness of B10.A(4R) mice to p46-61 is not due to non-major histocompatibility complex genes because B10.A mice (A[k], E[k]) respond well to p46-61. Interestingly, B10.A(4R) mice can raise a good proliferative response to p46-61 (R61A) (in which the arginine residue at position 61 (R61L/F/N/K), indicating that R61 was indeed responsible for hindering the interaction of p46-61 with the appropriate TCR. Finally, chimeric mice [B10.A(4R)-->B10.A] responded vigorously to p46-61, suggesting that thymic antigen presentation environment of the B10.A mouse was critical for development of a p46-61-reactive T cell repertoire. Thus, we provide experimental demonstration of a novel mechanism for unresponsiveness to a self peptide, p46-61, in the B10.A(4R) mouse owing to hindrance: in this system it is the interaction between the available TCR and the A(k)/p46-61 complex, which is hindered by epitopic residue(s) within p46-61. We argue that besides possessing T cells that are hindered by R61 of p46-61, CBA/J and B10.A mice have developed an additional subset of T cells bearing TCRs which are not hinderable by R61, presumably through positive selection with peptides derived from class II E(k), or class I D(k)/D(d) molecules. These results have important implications in self tolerance, shaping of the T cell repertoire, and in defining susceptibility to autoimmunity.
Moudgil
K D
KD
Department of Microbiology and Molecular Genetics, University of California, Los Angeles 90095-1489, USA.
Grewal
I S
IS
Jensen
P E
PE
Sercarz
E E
EE
D000595:Amino Acid Sequence; D000818:Animals; D000938:Antigen-Presenting Cells; D000939:Epitopes; D006649:Histocompatibility Antigens / Q000276:immunology* / Q000378:metabolism; D007108:Immune Tolerance; D008213:Lymphocyte Activation; D008285:Major Histocompatibility Complex; D051379:Mice; D008815:Mice, Inbred Strains; D008969:Molecular Sequence Data; D009113:Muramidase / Q000276:immunology*; D010446:Peptide Fragments / Q000276:immunology* / Q000378:metabolism; D011485:Protein Binding; D011828:Radiation Chimera; D011948:Receptors, Antigen, T-Cell / Q000276:immunology* / Q000378:metabolism; D013154:Spleen / Q000166:cytology / Q000276:immunology
D000939:Epitopes; D006649:Histocompatibility Antigens; D010446:Peptide Fragments; D011948:Receptors, Antigen, T-Cell; D009113:Muramidase