Specific deletion of the J-C delta locus in murine alpha/beta T cell clones and studies using transgenic mice.

A deletion event in the T cell receptor (TcR) delta locus has been characterized in a panel of mouse alpha/beta cytotoxic T lymphocyte (CTL) clones. Data presented here shows that J delta 1, J delta 2 and C delta are absent from functional CTL clones while a germ-line D delta 1 fragment is retained, thus suggesting a specific deletion of this region. We have investigated the possible significance of the J-C delta deletion by generating T cell lines from TcR alpha/beta transgenic mice. Unlike control T cell lines which included a T cell line derived from a beta transgenic mouse, the lines expressing the transgenic alpha/beta heterodimer have not deleted the C delta region. This strongly suggests that the J-C delta deletion event is not responsible for directing T cells to the alpha/beta lineage, but rather is involved in the rearrangement or transcriptional activity of the alpha locus. In addition, to ensure that the alpha/beta transgene does not have any inhibitory affects on the rearrangement of the delta loci in general, the gamma/delta expressing dendritic epithelial T cell (DETC) population was examined in TcR alpha/beta transgenic mice and alterations in this T cell subset were not found. This finding that normal gamma/delta DETC cells are present in alpha/beta transgenic mice, together with the data showing that the D delta 1 region remains in an unrearranged germ-line configuration in functional alpha/beta CTL, suggests that commitment to the alpha/beta or gamma/delta lineage is predetermined at a particular stage in early T cell ontogeny.

Ablation of "tolerance" and induction of diabetes by virus infection in viral antigen transgenic mice.

To address the mechanisms of tolerance to extrathymic proteins, we have generated transgenic mice expressing the lymphocytic choriomeningitis viral (LCMV) glycoprotein (GP) in the beta islet cells of the pancreas. The fate of LCMV GP-specific T cells was followed by breeding the GP transgenic mice with T cell receptor transgenic mice, specific for LCMV and H-2Db. These studies suggest that "peripheral tolerance" of self-reactive T cells does not involve clonal deletion, clonal anergy, or a decrease in the density of T cell receptors or accessory molecules. Instead, this model indicates that self-reactive cytotoxic T cells may remain functionally unresponsive, owing to a lack of appropriate T cell activation. Infection of transgenic mice with LCMV readily abolishes peripheral unresponsiveness to the self LCMV GP antigen, resulting in a CD8+ T cell-mediated diabetes. These data suggest that similar mechanisms may operate in several so-called "T cell-mediated autoimmune diseases."