Discovering Immunity: Identification of genes involved in phagocytosis. B.R. Soper , K.V. Anderson. Molecular Biology Program, Sloan-Kettering Institute, New York, NY.

   The Drosophila immune system can recognize microbial organisms as foreign and mount defense responses to eliminate those pathogens. One important aspect of recognition of non-self organisms in the innate immune response is the removal of pathogens via phagocytosis.
   Drosophila macrophages, or plasmatocytes, can internalize GFPuv expressing E. coli extremely rapidly, within 30 seconds. Internalized, lysed bacteria are present within the macrophages as visualized by standard and confocal fluorescent microscopy. Cdc42 and shi alleles fail to internalize bacteria, as might be expected from data implicating these genes as being essential for mammallian phagocytosis and Drosophila endocytosis, respectively. To identify genes required for pathogen recognition and internalization, we performed a screen for phagocytosis deficient ("dysphagic") mutants on the X chromosome. 1401 adult viable lines carrying new EMS induced X-linked mutations were assayed. We identify 30 mutants failing to internalize fluorescent E. coli. All the mutants also fail to internalize S. cerevisiae and B. subtilis, suggesting that they have a general defect in phagocytosis. Mapping and detailed phenotypic analysis are in progress.