A Self-Destructing Cell Type Found in Planarians Can Kill Other Cells and Bacteria
- 演化之聲
- Jul 12
- 4 min read
The Mediterranean planarian Schmidtea mediterranea is a highly regenerative flatworm belonging to the phylum Platyhelminthes. Its body contains a population of cells known as neoblasts, which are adult stem cells and form the foundation of planarian tissue turnover and regenerative capacity. These cells divide continuously, replenishing cells that must be replaced throughout the body and supplying new cells required for regeneration after injury.
Yet this remarkable regenerative ability also creates a special biological burden. When an animal carries a large population of continuously dividing cells, mutations, signaling imbalance, abnormal differentiation, or pathogen infection can have long-lasting consequences. Planarians therefore need a defensive system capable of dealing with aberrant cells, regenerative cell sources, and infectious threats. Previous studies had already shown that planarians possess an innate immune system, but lack an adaptive immune system. They also contain cathepsin-expressing phagocytic cells. However, these known immune functions could not fully explain how planarians rapidly and broadly eliminate dangerous sources within the body. This raised a deeper question: what hidden immune mechanisms still remain undiscovered in planarians?
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