Phagocytosis in Drosophila melanogaster Immune Response

Abstract

Analysis of phagocytosis in Drosophila has been greatly facilitated by the characterization of the phagocytic properties of S2 cells, an embryonic hemocyte-derived cell line that is readily amenable to RNA-mediated interference (RNAi), opening the field to systematic studies. Identification of new genes involved in phagocytosis relies either on genome-wide RNAi screens in S2 cell culture, proteomic analysis of the plasmatocyte phagosome, or in silico homology screening. An eater loss-of-function mutation has been generated, showing that Eater is required for phagocytosis of several types of bacteria in vivo. The second important conclusion from this brief overview of D. melanogaster phagocytic receptors concerns the high redundancy in the receptors. Phagocytosis contributes to the natural defenses of insects against all microorganisms, including bacteria, yeast, and parasites, but has mainly been studied in the case of bacteria. The finding that many bacteria proliferate in the circulatory cavity of mutant flies lacking hemocytes demonstrated the role of phagocytosis. This chapter illustrates that in Drosophila phagocytosis plays a major role in the removal of microorganisms following any type of infections. Understanding the resistance of intracellular bacteria to phagocytosis and identification of the receptors for their uptake will be of special interest. The major challenge is to decipher the relationships between cellular and humoral responses and the relative contribution of phagocytosis and AMP bacterial killing in various infection models.