Tatsumi Nakano

Biochemical basis of antigen-specific suppressor T cell factors: controversies and possible answers.

Publisher Summary The chapter reviews previous observations made on T-suppressor factor (TsF) and provides interpretations for controversial issues on this factor. Antigen-specific T cell-mediated immunosuppression could be transferred from one animal to other syngeneic animals either with intact suppressor cells or with soluble factors derived from the cells. The chapter also discusses the experiments that provide the evidence that OVA-specific glycosylation inhibiting factor (GIF), which is an effector type TsF, consists of the 55-kDa TCRa chain-GIF conjugate and the TCRP chain. After the identification of T cell receptors (TCR) on helper and cytotoxic T cells, however, fundamental questions can be raised on T cell-mediated suppression with the failure to identify TCR and TCR gene rearrangement in representative Ts hybridomas. In addition, the ability of Ts cells and antigen-specific TsF to bind specifically to nominal antigen, independently of major histocompatibility complex (MHC) gene products, created skepticism on the nature of Ts cells and the origin of TsF.

Preparation of soluble recombinant T cell receptor α chain by using a calmodulin fusion expression system

We have isolated a full length T cell receptor alpha chain (TCR alpha) cDNA derived from a bee venom phospholipase A2-specific mouse suppressor T cell hybridoma. A bacterial fusion expression system was constructed using rat calmodulin as a fusion partner for production of soluble TCR alpha. In this system, calmodulin-TCR alpha fusion protein was expressed at a high level in the soluble fraction of bacterial cell lysate, and could be purified by binding of calmodulin portion of the protein to phenyl-Sepharose. Using this system, fusion proteins containing a TCR alpha peptide corresponding to the complete extracellular region, V alpha-J alpha region or C alpha extracellular region were isolated. TCR alpha peptides were then released from the fusion proteins by digestion with thrombin which recognizes a linker sequence between calmodulin portion and TCR alpha segment. Polyclonal antibodies against constant region of TCR alpha chain (C alpha) were obtained by immunization of rabbits with the recombinant C alpha peptide. ELISA for TCR protein was established by using the polyclonal antibodies and the monoclonal antibody specific for C alpha region.

Controversial Issues and Possible Answers on the Antigen-Specific Regulation of the IgE Antibody Response

In the past 10 years, the major approaches for the regulation of the IgE antibody response by many investigators have been focused to isotype-specific suppression of the IgE synthesis. However, another approach to be considered is to suppress the antibody response to the allergens to which the allergic patients are sensitive. In this presentation, we would like to discuss the possibility to regulate the antibody response in antigen-specific manner, and scientific evidence for the presence of such a mechanism.