Amazing stuff!
"In brief
- ... scientists uncovered a new type of cytotoxic cell called “ruptoblasts” in experiments with planarian flatworms.
- Unlike common blood-derived immune cells, ruptoblasts are specialized gland cells that undergo an explosive cell death called "ruptosis” when triggered by a specific hormone.
- A single ruptoblast can kill dozens of target cells within minutes through an explosion of toxic agents that quickly dissipate.
- Ruptosis is the most explosive form of cell death known to date, making it distinct from all previously described cell death pathways.
... scientists have discovered a new type of immune cell that kills surrounding cells via explosion – a cellular detonation so fast and complete that the cell vanishes within minutes, leaving no trace behind. This discovery comes from an unlikely source: planarian flatworms. ..."
From the highlights and abstract:
"Highlights
• Ruptoblasts are a cytotoxic glandular cell type likely conserved across bilaterians
• Activin triggers explosive ruptosis via ER calcium amplified through the cytoskeleton
• Ruptoblasts drive tissue rejection in planarian chimeras and aid bacterial clearance
• Ruptosis releases potent broad-spectrum cytotoxic agents
Summary
Current understanding of cytotoxic immunity is shaped by hematopoietic-derived cells—T cells, natural killer cells, and neutrophils.
Here, we identify “ruptoblasts,” a previously unknown cytotoxic glandular cell type in regenerative planarian flatworms. Ruptoblasts undergo an explosive cell death, “ruptosis,” triggered by activin, a multifunctional hormone acting as an inflammatory cytokine.
Excessive activin—induced through protein injection, genetic chimerism, or bacterial infection—initiates ruptosis, discharging potent diffusible cytotoxic agents capable of eliminating nearby cells, bacteria, and even mammalian cells within minutes.
Ruptoblast ablation suppresses inflammation but compromises bacterial clearance, highlighting their broad-spectrum immune functions.
Mechanistically distinct from known cytotoxic and cell death mechanisms, the explosive nature of ruptosis relies on endoplasmic reticulum (ER)-derived calcium and cytoskeleton-dependent signal amplification.
Ruptoblast-like cells appear conserved in diverse basal bilaterians, implying an ancient evolutionary origin. These findings unveil a strategy coupling hormonal regulation with immune defense and expand the landscape of evolutionary immune innovations."
Explosive cytotoxicity of ruptoblasts bridges hormone surveillance and immune defense (no public access)
Graphical abstract
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