SELECTION FOR AMINO-ACID-SEQUENCE AND J-BETA-ELEMENT USAGE IN THE BETA-CHAIN OF DBA 2V BETA(B)-DERIVED AND DBA 2V BETA(A)-DERIVED MYOGLOBIN-SPECIFIC T-CELL CLONES

Previous experiments in our laboratory have demonstrated that there is a marked restriction on the TCR beta-chain usage in DBA/2 mice in res ponse to the sperm whale myoglobin (SpWMb) determinant 110-121, predom inated by the use of the Vbeta8.2 gene element. We analyzed the respon se of mice that had been genetically depleted of Vbeta8+ T cells by ge nerating a DBA/2 line that carries the Vbeta(a) TCR haplotype. Despite the very limited TCR repertoire expressed by DBA/2Vbeta(a) mice, they made an excellent response after immunization with the SpWMb 110-121 peptide. Data presented in this manuscript demonstrate that there is a n equally restricted TCR Vbeta-chain utilization in the T-cell respons e to the determinant SpWMb 110-121 in DBA/2Vbeta(a) mice. Unexpectedly , there was a shift of MHC restriction of this determinant to T cells in the Vbeta(a) strain when compared with the Vbeta(b) strain of DBA/2 mice. We had previously demonstrated that DBA/2 mice utilized both th e hybrid Ealpha(d)Abeta(d) MHC molecule as well as the conventional Aa lpha(d)Abeta(d) molecule as presenting elements in response to SpWMb 1 10-121. Data presented in this manuscript demonstrate that the T-cell response in DBA/2Vbeta(a) mice is entirely restricted by the Aalpha(d) Abeta(d) MHC class II molecule. By analyzing a panel of SpWMb 110-121- specific T-cell clones from DBA/2Vbeta(a) mice, we were able to study the TCR repertoire expressed on T cells from mice that lack the Vbeta8 .2 gene. The Vbeta usage by the panel of clones analyzed was remarkabl y homogeneous. Thirteen of the 17 clones analyzed used the Vbeta1 gene segment. Perhaps more striking was the junctional region nucleotide a nd amino acid sequences that were shared among these clones and that w ere similar to the Vbeta8.2 clones analyzed previously. All clones ass ayed used the Jbeta2.6 element, as did the great majority of the Vbeta 8.2 clones analyzed from DBA/2 (and B10.D2) Vbeta(b) mice. Importantly , in each strain of mice, irrespective of the Vbeta utilized, each TCR appeared to have selected an acidic amino acid in the beta-chain at p osition 100. By analyzing the relationship between the structure of th e TCR beta-chain and T-cell functional specificity, utilizing a panel of monosubstituted peptides, it has been possible to suggest structure /function relationship between TCR elements and specific amino acid re sidues in the determinant SpWMb 110-121.