Researchers at the Institute of Medical Microbiology and Hygiene aim to elucidate host pathogen interactions to provide a basis for the development of new strategies to fight infectious diseases. Current research at the Institute has evolved over decades: the nineteen-sixties through nineteen-eighties, under the leadership of P. Klein, heralded an era of pioneering studies on complement, interleukins and T-cells, with bacterial virulence factors and molecular biology of viruses emerging as additional themes in the nineteen-eighties. From 1990 until early 2012 the Institute was led by S. Bhakdi, whose research focused on bacterial pore forming toxins and complement. During these two periods, the Institute also served as an important coordinator of Collaborative Research Centers in the field of Immunology. Between September 2013 and October 2016, A. Diefenbach held the position as director of the Institute; and a new class of lymphoid cells became the main area of investigation. Thus, for more than 50 years, Immunology has been at the heart of the Institute´s research activities. In continuation of this tradition, and driven by the quest for the New, current groups explore cell autonomous responses to microbes, aiming to unravel their role for host resilience to infections.