This immunofluorescence image shows macrophages expressing the activating receptor N KG 2 D (red). The nuclei are counterstained with a blue fluorochrome (DA P I). N K G2D is a recently cloned activating receptor on murine and human NK cells, macrophages and cytotoxic T cells. As the newly identified ligands for this receptor are exclusively expressed on tumor cells and presumably on infected cells, this receptor may be important to initiate anti-tumor and anti-viral responses during innate and acquired immunity. This work is ongoing in the laboratory of Professor David H. Raulet with postdoctoral fellow Dr. Andreas Diefenbach in the Department of Molecular and Cell Biology.