What would happen if one immune cell exploded like a small bomb, destroying dozens of surrounding immune cells? That’s exactly what a Stanford team discovered while studying planarian flatworms, tiny creatures known for their extraordinary ability to regenerate lost body parts. Scientists have discovered a new type of immune cell called “ruptoblasts” that protect the body by violently bursting and releasing toxic substances into the surrounding environment. Within minutes, these cells can wipe out dozens of nearby cells and then disappear completely, leaving virtually no trace. The discovery provides a rare glimpse into an ancient immune strategy that may have existed long before more familiar defense systems such as white blood cells evolved.
Stanford researchers discover an immune cell that kills cells by self-destructing
The discovery began with a simple question: Can flatworms distinguish their own tissues from those of other worms? Researchers in the lab of Bo Wang, associate professor of bioengineering at Stanford University, set out to answer this question by cutting planarian flatworms longitudinally and fusing them with tissue taken from different worms.The flatworm species used in these experiments, Schmidtea mediterranea, has long fascinated biologists because of its ability to regenerate its entire body from a small fragment of tissue. But when Chew Chai, a postdoctoral researcher in Wang’s lab, created these “Frankenstein” worms, she found that the animals rejected tissue from unrelated worms, a process similar to human organ transplant rejection.Flatworms do not rely on immune defenses similar to humans, but respond in an entirely different way. While examining the rejected tissue under a microscope, Chai noticed that the cells disappeared almost immediately, leaving a trail of dead cells. After ruling out errors in their experiments, the team realized they had stumbled upon a previously unknown immune cell type, which they named “ruptoblasts.”“
How ruptured mother cells trigger ‘rupture’ to destroy nearby cells
according to The research is published in the journal Cellnucleation is triggered by activin, a hormone known to play an important role in flatworm biology, regulating regeneration and reproduction.When activin levels spike, usually due to tissue rejection, infection, or injury, the ruptured mother cells respond by undergoing rapid cell death, which the researchers name “rupture.” The cell’s calcium levels rise dramatically, causing it to burst within seconds to minutes, releasing a cocktail of toxic substances that kill nearby cells before the ruptured mother cell itself disappears completely.What was particularly unusual about the rupture was its rapidity. Other organisms, including some mammalian cells and bacteria, are known to undergo explosive cell death, but these deaths typically unfold over several hours as the cell contents slowly leak out through the pores. In contrast, apoptosis occurs almost immediately, which according to the researchers makes it the fastest form of explosive cell death recorded to date.
Why planarian flatworms demonstrate unprecedented immune defenses
Ruptoblasts are significantly different from immune cells found in humans and other vertebrates. T cells, natural killer cells, and neutrophils, the cells most relevant to mammals fighting infections, are all hematopoietic cells, meaning they originate in the bone marrow. However, nucleoblasts are glandular cells that appear to repurpose their secretory machinery for an entirely different, more destructive purpose.When the team looked for similar cells in other animals, they found phragmocyte-like cells only in basal bilaterians, which include flatworms and diverged from the vertebrate lineage hundreds of millions of years ago. research paper. This suggests that rupture may represent an ancient immune strategy that was eventually lost in vertebrates during evolution.One theory is that mammals simply cannot withstand such defenses. Rupture causes localized tissue damage, which flatworms can quickly repair thanks to their abundant stem cells and remarkable regenerative abilities. Vertebrates that lack the same regenerative capacity may have evolved milder immune strategies.
What phragmocytes mean for future medical treatments
To test just how powerful the nucleated cells were, the researchers exposed them to E. coli, human kidney cells, and mouse blood cells. In each case, the ruptured cells successfully destroyed their targets.Crucially, the damage remained highly localized. There is no chain reaction that spreads to surrounding cells, and there is no lasting toxicity once the mother cell ruptures and disappears. Senior author Bo Wang said that this precision makes this discovery particularly exciting from a medical perspective, as it could potentially be used to design targeted treatments for bacterial infections and even tumors without damaging healthy surrounding tissue. For details, see Stanford University official report About the findings.Currently, this finding highlights how little is known about the immune system outside of a few well-studied species. As Wang said, the countless animals living in environments teeming with bacteria and viruses may rely on immune mechanisms that scientists have yet to begin to study. By studying unconventional organisms like planarians, researchers hope to discover entirely new biological strategies that could eventually inspire new ways to tackle medicine’s toughest challenges, from infections to cancer.
