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We have constructed mice containing the human V beta 3 TCR gene from the influenza virus haemagglutinin specific human CD4+ T cell clone HA1.7. Similar cell yields were obtained from transgenic and non-transgenic lymphoid tissue, with normal levels of T cells and with no unusual bias of the CD4 or CD8 subpopulations. Immunostaining and FACS analysis of transgenic thymocytes, spleen, and mesenteric lymph nodes revealed that the majority of T cells expressed the human V beta 3 TCR on the cell surface. Small numbers of cells expressing murine TCR beta chain were also detected. Polymerase chain reaction analysis revealed that an extensive V alpha TCR repertoire was used in the human V beta 3 transgenic mice. Lymphocytes from the spleen and mesenteric lymph nodes of transgenic mice were assessed for functional activity in vitro. Isolated cells were stimulated with mitogen or superantigen, as well as directly through the TCR-CD3 complex, and their ability to proliferate and secrete lymphokines analysed. Cells from transgenic mice responded well after stimulation with phytohaemagglutinin, concanavalin A, anti-CD3 antibody, anti-CD3 antibody with phorbol ester, and Staphylococcus aureus enterotoxin B, and also showed alloreactivity in a mixed lymphocyte reaction. Minimal levels of response were detected after stimulation with murine TCR beta antibody. Together, these data suggest that a human TCR beta chain is able to associate with a murine TCR alpha chain, to form a fully functional surface TCR-CD3 complex.

We have recently identified and cloned TCF-1, a T cell-specific transcription factor with specificity for the AACAAAG motif in the CD3 epsilon enhancer and for the TTCAAAG motif in the TCR alpha enhancer. TCF-1 belongs to the family of transcription-regulating proteins which share a region of homology termed the HMG-box. Here, we show by gel retardation analysis that TCF-1 specifically recognizes the T beta 5 element of the TCR beta enhancer and the T delta 7 element of the TCR delta enhancer. Comparison of the sequences of all elements recognized by TCF-1 defines a consensus motif A/T A/T C A A/G A G. These observations imply that TCF-1 is involved in the control of several T cell-specific genes and might thus play an important role in the establishment and maintenance of the mature T cell phenotype.