Whereas Vδ2 T cells respond to bacterial infections through reactivity to prenyl antigens (21), Vδ1 T cells have been implicated in viral clearance of infections caused by cytomegalovirus (22) and Epstein Barr virus (23) as well as a number of transformed cell lines (24) through secretion of IFN-γ. This evidence concerns the gene IFNG and bacterial infectious disease.