A Cre-loxP based system for studying horizontal gene transfer.

We have previously shown that DNA can be transferred to phagocytosing cells via the uptake of apoptotic cells. We report a model system that facilitates study of antigen presentation of genes transferred specifically via horizontal gene transfer. Constructs were generated encoding the LacZ gene or the influenza A nucleoprotein silenced by a STOP sequence flanked by two loxP sites. These reporter genes were demonstrated to be silent in donor cells and become activated after phagocytosis of Cre-expressing fibroblasts or macrophages. These results provide a model system for studying the influence of horizontally transferred antigens on activation of the immune system.