The immune system combats a broad variety of pathogens as well as toxins and tumor cells through complex interactions of cells and proteins. One part of the immune system, the innate immune system, is composed of several distinct components including immune cells like macrophages, monocytes, granulocytes and natural killer (NK) cells. NK cells are regulated by a complex balance between several activating and inhibitory receptors, e.g., NKp80. The crosstalk between NKp80 and its ligand AICL may play a crucial role in immunosurveillance of viral and bacterial infections, malignancy, and the pathogenesis of autoimmune diseases, but the signal-transducing elements associated with NKp80 or AICL have not yet been defined. The aim of this thesis was to find an effective expression system for NKp80 and its ligand AICL to enable a crystallization screen. Protein crystallization is the common method to get the 3D structure of proteins.