A Newly Discovered Immune Cell Defends the Body by Exploding

A previously unknown type of immune cell that destroys threats by literally erupting has been identified by scientists at Ben-Gurion University of the Negev (BGU) and Stanford University. The cells, named ruptoblasts, operate through a mechanism not previously seen in immune biology and belong to a glandular cell lineage rather than the white blood cell lineage that conventional immune defense is built on. The findings appear in Cell.

Ruptoblasts were discovered in flatworms and act like cellular grenades. When they detect a spike in activin—a hormone that functions as a distress signal—a rapid chain reaction unfolds within minutes: the cell floods with calcium, triggering an eruption that releases a wave of broad-spectrum killing agents capable of destroying everything in the immediate blast zone.

The team demonstrated two distinct protective roles for this eruption. When flatworms were infected with dangerous bacteria, neighboring immune cells released the activin signal, detonating nearby ruptoblasts whose blast wave rapidly shattered the membranes of the invading microbes. The cells also play a role in tissue rejection: when tissues from two different flatworms were fused together, the resulting activin buildup triggered mass eruptions and tissue lesions. Genetically removing the ruptoblasts halted the rejection response entirely.

The chemical cocktail released by exploding ruptoblasts also proved potent against mammalian cells in lab tests, including human cancerous kidney cells—suggesting the killing agents are not species-specific.

Despite their destructive capacity, ruptoblasts have built-in controls. If a ruptoblast is mechanically crushed or killed, it releases no toxins; the killing agents require the precise biochemical trigger of activin to become lethal. Neighboring ruptoblasts caught in a blast zone do not set off a chain reaction, and the toxic footprint breaks down within 15 minutes.

Genetic mapping showed that ruptoblasts are absent in standard laboratory models such as mice and fruit flies but are present across a wide range of ancient, primitive organisms, pointing to a deep evolutionary history.

"These findings reveal a completely new strategy that directly links hormonal signals with explosive immune defense," the authors note. "It shows how diverse nature can be when inventing ways to fight off infection and could eventually inspire new ways to engineer cellular therapies to target bad bacteria or malfunctioning cells."