Robert Markus and Ulrich Theopold
In order to retain body integrity, multicellular organisms have to distinguish between self and non-self to protect themselves from other organism. The defending structures involve physical barriers, humoral and cellular elements, which share tasks during the major stages of immunity: recognition, translation of the recognition-signal and production of effector molecules. Although invertebrates like Drosophila rely mostly on innate immunity, they successfully inhabit most of the environments on earth. In addition Drosophila provides many genetic tools and can be easily manipulated. Furthermore many molecular and imaging tools to study the immune processes against microorganism and parasites have been optimized for use in Drosophila. Examples where the roles of the genes and molecules involved in immune reactions against bacteria, parasitoid wasps and entomopathogenic nematodes were deciphered will be presented.