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Published on: January 9, 2019
Engulfed pathogen-induced apoptosis in haemocytes of giant freshwater prawn, Macrobrachium rosenbergii
1Graduate Institute of Veterinary Pathology, National Chung-Hsing University, Taichung, Taiwan.
Abstract:
Haemocytes of the giant freshwater prawn, Macrobrachium rosenbergii, were investigated for the induction of apoptosis after phagocytosis of pathogenic yeasts, bacteria and non-pathogenic latex beads in vitro. Isolated haemocytes of M. rosenbergii were cultured at a ratio of 1:50 haemocytes to pathogen with the yeast Debaryomyces hansenii, the bacteria Aeromonas hydrophila or Enterococcus faecium, or with latex beads at 25 degrees C for 2 h, followed by washing to remove free particles. At least 200 haemocytes were counted to determine the phagocytosis rate, and the results showed that haemocytes engulfed latex beads at a higher rate than the aquatic pathogens. By transmission electron microscopy, the yeast- or bacterium-engulfing haemocytes displayed morphological changes characteristic of apoptosis, including formation of cytoplasmic vacuoles, chromatin condensation and fragmentation of nuclei. This pathogen-induced apoptosis was further confirmed by DNA laddering and TUNEL (terminal deoxynucleotidyl transferase-mediated deoxy-UTP nick-end-labelling) assays. Neither haemocytes treated with latex beads nor uninfected haemocytes (control group) showed signs of apoptosis after 48 h in culture.
Insights
Giant freshwater prawn haemocytes undergo apoptosis when engulfing pathogens like yeast and bacteria. This programmed cell death, a key immune response, was confirmed using DNA laddering and TUNEL assays in Macrobrachium rosenbergii.
Area of Science:
- Aquatic immunology
- Crustacean cell biology
- Invertebrate pathology
Background:
- Haemocytes are crucial for invertebrate immunity, mediating phagocytosis and pathogen clearance.
- Understanding prawn immune responses is vital for aquaculture sustainability.
- Apoptosis, or programmed cell death, is a regulated cellular process involved in development and immunity.
Purpose of the Study:
- To investigate the induction of apoptosis in Macrobrachium rosenbergii haemocytes following phagocytosis of pathogens.
- To differentiate the cellular response to pathogenic versus non-pathogenic particles.
- To characterize the morphological and molecular evidence of apoptosis in prawn haemocytes.
Main Methods:
- Primary culture of M. rosenbergii haemocytes.
- In vitro incubation with Debaryomyces hansenii (yeast), Aeromonas hydrophila/Enterococcus faecium (bacteria), or latex beads.
- Phagocytosis rate determination via cell counting.
- Morphological analysis using transmission electron microscopy.
- Confirmation of apoptosis using DNA laddering and TUNEL assays.
Main Results:
- M. rosenbergii haemocytes exhibited higher phagocytosis rates for latex beads compared to pathogenic yeasts and bacteria.
- Haemocytes engulfing pathogens showed characteristic apoptotic morphological changes, including vacuolation and nuclear fragmentation.
- Pathogen-induced apoptosis was confirmed by DNA laddering and TUNEL assay results.
- No apoptosis was observed in haemocytes exposed to latex beads or in uninfected control cells.
Conclusions:
- Phagocytosis of pathogenic microbes induces apoptosis in Macrobrachium rosenbergii haemocytes.
- This pathogen-induced apoptosis represents a significant cellular immune mechanism in giant freshwater prawns.
- The findings contribute to understanding crustacean innate immunity and disease resistance.
