Thymus-independent T-cell differentiation in vitro

The generatation of large quantities of never human T-cell clones ex vivo would make a wide range of gene- and immune-therapies for tumours and viral infections possible. Several techniques have been described to generate, in vitro and in vivo (using xenogenic hosts), mature T cells from fetal-neonatal and adult human CD34(+) cells. All these techniques are cumbersome and cannot be easily translated into clinical protocols because they involve cocultivation of CD34(+) cells with thymic fragments from either human or murine fetuses. We report that the mononuclear cells of human cord blood contain a cell population that supports the differentiation of CD34(+) cells into CD4(+) or CD8(+) naive T cells in serum-deprived cultures stimulated with stem cell factor and interleukin 7. CD4(+) or CD8(+) CD45RA(+) TCR alpha beta(+) T cells were continuously produced in vitro over a period of 20 d under these conditions. The generation of T cells in these cultures was a dynamic process and crones of T cells expressing new T-cell receptor beta-chain rearrangments were generated over time. These results pace the way far the development of very simple culture conditions for ex-vivo production of naive helper or cytotoxic T cells which could be very useful for gene- and immune-therapy of human diseases.