Generation of a conditionally neo(r)-containing retroviral producer cell line: effects of neo(r) on retroviral titer and transgene expression.

We have developed a method for generating high-titer retroviral producer cell lines conditionally containing a neomycin resistance gene (neo(r)) based on the Cre/loxP system. For this, a bicistronic retroviral splicing vector carrying the green fluorescence protein (GFP) and a marker gene cassette consisting of internal ribosome entry site (IRES) and neo(r) flanked by loxP sites, was constructed and conveniently used to generate a G418 resistant vector producer cell line. Following titer determination and verification of the biological activity of the retroviral supernatants, the selectable expression cassette which was no longer required was excised from the provirus by transient Cre expression using an adenoviral vector.

Transgenic mice demonstrate that epithelial homing of gamma/delta T cells is determined by cell lineages independent of T cell receptor specificity.

gamma/delta T cells with different TCR repertoires are compartmentalized in different epithelia. This raises the possibility that the TCR-gamma/delta directs homing of T cells to these epithelia. Alternatively, the signals that induce TCR-gamma/delta expression in developing T cells may also induce homing properties in such cells, presumably in the form of cell surface receptors.

Recognition of a self major histocompatibility complex TL region product by gamma delta T-cell receptors.

Ligand specificity of a murine gammadelta T-cell receptor-expressing hybridoma (KN6) derived from adult thymocytes has been analyzed in detail. The molecule recognized by the KN6 gammadelta T-cell receptor is expressed on syngeneic cells of various sources (peritoneal macrophages, thymocytes, spleen cells, and Abelson murine leukemia virus-transformed cell lines) and on transformed cells arrested at an early stage of development (e.g.

Different gamma delta T-cell receptors are expressed on thymocytes at different stages of development.

We have analyzed the structural diversity of the murine gamma delta T-cell receptor (TCR) heterodimer expressed on CD4- CD8- thymocyte populations and on TCR gamma delta-expressing hybridomas derived from thymocytes of fetal, newborn, and adult mice. We found that CD4- CD8- thymocytes derived from mice of different pre- and postnatal age preferentially express a gamma delta TCR encoded by different subsets of gamma and delta gene segments. This age-dependent differential expression of gamma delta TCR on thymocytes seems to be accomplished in part by a specific control of rearranged gamma genes operating at the level of transcription and/or RNA stability.