Hemolymph-dependent and -independent responses in Drosophila immune tissue

J Cell Biochem. 2004 Jul 1;92(4):849-63. doi: 10.1002/jcb.20123.

Abstract

Insects possess an antimicrobial defense response that is similar to the mammalian innate immune response. The innate immune system is designed to recognize conserved components of microorganisms called pathogen-associated molecular patterns (PAMPs). How host receptors detect PAMPs and transmit the signals to mount the immune response is being elucidated. Using GFP-Dorsal, -Dif, and -Relish reporter proteins in ex vivo assays, we demonstrate that Drosophila fat bodies, a major immune tissue, have both hemolymph-dependent and -independent responses. Microbial preparations such as lipoteichoic acid (LTA) and peptidoglycan (PGN) can stimulate some responses from dissected and rinsed larval fat bodies. Therefore, at least some aspects of recognition can occur on fat body cell surfaces, bypassing the requirement of hemolymph. Our results also show that supernatants from bacterial cultures can stimulate the nuclear translocation of Dorsal in dissected fat bodies, but this stimulation is strictly hemolymph-dependent. Various biochemical assays suggest that the factors from bacterial supernatants that stimulate the hemolymph-dependent nuclear translocation are likely made up of proteins. We further show that Dorsal mutant larvae have much lower phenoloxidase activity, consistent with a more important role of Dorsal in innate immunity than previously shown.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Animals, Genetically Modified
  • Carrier Proteins / metabolism
  • Cell Nucleus / metabolism
  • DNA-Binding Proteins / metabolism
  • Drosophila Proteins / metabolism
  • Drosophila melanogaster / embryology
  • Drosophila melanogaster / immunology*
  • Drosophila melanogaster / microbiology
  • Fat Body / immunology*
  • Fat Body / metabolism
  • Fat Body / microbiology
  • Female
  • Green Fluorescent Proteins / metabolism
  • Hemolymph / immunology*
  • Immunity, Innate*
  • Lactobacillus casei
  • Larva / immunology
  • Larva / metabolism
  • Larva / microbiology
  • Lipopolysaccharides / pharmacology
  • Male
  • Monophenol Monooxygenase / metabolism
  • NF-kappa B / metabolism*
  • Nuclear Proteins / metabolism
  • Phosphoproteins / metabolism
  • Protein Transport
  • Recombinant Fusion Proteins / metabolism
  • Teichoic Acids / pharmacology
  • Transcription Factors / metabolism

Substances

  • Carrier Proteins
  • DNA-Binding Proteins
  • Dif protein, Drosophila
  • Drosophila Proteins
  • Lipopolysaccharides
  • NF-kappa B
  • Nuclear Proteins
  • Phosphoproteins
  • Recombinant Fusion Proteins
  • Rel protein, Drosophila
  • Teichoic Acids
  • Transcription Factors
  • dl protein, Drosophila
  • peptidoglycan recognition protein
  • Green Fluorescent Proteins
  • lipoteichoic acid
  • Monophenol Monooxygenase