T cell antigen receptor and chain genes and MHC restriction

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1. The T cell receptor (TcR) is composed of <alpha> and <beta> chains. By transferring cloned and <beta> chain genes, it was established that this <alpha><beta> heterodimer is responsible for the dual specificity of T cells. However, it is still not known which amino acid residues are important in determining T cell specificities.In order to define important amino acid residues, we derived mutant T cell clones with altered specificities from an I-A^K reactive T cell clone, MS202. One mutant clone, E-3, was shown to respond to I-A^D and I-A^d as well as I-A^K. It seemed that this specificity change was due to the structural change of TcR in E-o as molecular weight of TcR was smaller in E-3 than in MS202. However, nucleotide sequences of TcR <alpha> and <beta> chain genes were identical between MS202 and E-3. It was found that E-3 has a defect in glycosylation. In addition, these two clones might express two kinds of TcR molecules with different chains. We are in a process of determining the cause of specificity change in E-3.2. All murine suppressor T cell clones examined were shown to express TcR <alpha> and <beta> chain genes. We are now in a process of cloning genes specifically expressed in suppressor T cells using the subtraction hybridization.3. The amount of mRNA coding for TcR <alpha> and <beta> chains was found to be almost constant whether T cells are activated by antigens or not.4. The TcR <beta> chain gene of NZW mice seems to contribute to the autoimmunity in (NZB x NZW)F_1 mice.