The research programme pursued in the context of the Graduate School “Molecules of Infection IV” (MOI IV) focuses on elucidating (i) the complex interactions between pathogen and host and (ii) the mechanisms that control immunological responses to infectious diseases. The ultimate goal of this research is to develop strategies for the effective elimination of invasive pathogens and the suppression of the damage they cause to tissues. MOI IV thus represents a continuation and extension of the successful lines of research undertaken during the first three funding periods MOI I – MOI III. The 18 projects of MOI IV concentrate on the identification and characterization of molecules that play significant roles in the infection process initiated by specific pathogens that provide tractable experimental models. The insights gained during the lifetime of MOI IV will undoubtedly broaden the scope of current concepts of infection biology.  The 18 projects submitted for MOI IV fall into four interlinked thematic fields.