The cell-mediated immunity of Drosophila melanogaster: Hemocyte lineages, immune compartments, microanatomy and regulation

In the animal kingdom, innate immunity is the first line of defense against invading pathogens. The dangers of microbial and parasitic attacks are countered by similar mechanisms, involving the prototypes of the cell-mediated immune responses, the phagocytosis and encapsulation. Work on Drosophila has played an important role in promoting an understanding of the basic mechanisms of phylogenetically conserved modules of innate immunity. The aim of this review is to survey the developments in the identification and functional definition of immune cell types and the immunological compartments of Drosophila melanogaster. We focus on the molecular and developmental aspects of the blood cell types and compartments, as well as the dynamics of blood cell development and the immune response. Further advances in the characterization of the innate immune mechanisms in Drosophila will provide basic clues to the understanding of the importance of the evolutionary conserved mechanisms of innate immune defenses in the animal kingdom.