In our research topic ecology, transmission and pathogenicity of Legionella pneumophila, we analyze the pathogen-host interactions of the causative agent of Legionnaires ́s disease. In addition to protozoa, nematodes and human cells we study the infection of human lung tissue explants. Special emphasis is placed on the protein-protein interactions of the L. pneumophila macrophage infectivity potentiator protein Mip (peptidyl-prolyl-cis/trans-isomerases) and zinc metalloprotease ProA with host cell structures.