Summary
Modern gene editing, high-resolution imaging and omics tools have expanded cell biology beyond the two classic forms of cell death. Researchers are also finding that some cells can delay death or recover after a death programme begins.
Scientists are finding that cells have many more ways to die than biology textbooks traditionally described—and that death is not always an immediate, irreversible endpoint. Research since 1999 has identified roughly 20 additional forms of cell death, with at least four new types defined in 2025 alone.
The expanding catalogue matters because the route a cell takes to die can influence neighbouring cells, tissues and the immune system. It may also offer researchers new ways to destroy cancer cells, reduce harmful inflammation or protect cells in damaged organs.
From two classic pathways to a wider map
For much of modern biology, cell death was divided into two broad categories. Necrosis was understood as an accidental form of destruction, caused when a cell was crushed, cut or otherwise damaged. Apoptosis, by contrast, was considered a controlled sequence in which a cell dismantles itself and releases small membrane structures that can be cleared by the immune system.
New technologies have made it easier to distinguish the molecular routes behind cell death. Gene editing can reveal which genes are required, high-resolution imaging can show how a cell changes, and “omics” techniques can measure broad changes in its molecules.
The resulting pathways include pyroptosis, a fiery and inflammatory form of death; necroptosis, which can rupture a cell and activate immune responses; and ferroptosis, in which iron-dependent chemical reactions damage the cell membrane. Other examples are linked to excess copper, sodium overload or unusually alkaline conditions inside the cell.
The alkaline form, named alkaliptosis, was identified when cancer cells in laboratory dishes died even though researchers could not assign their death to known pathways. The cells had an unusually high internal pH, meaning they had become too basic. That result points to cellular pH as a possible target for cancer research, although the work describes a biological mechanism rather than an established treatment.
Researchers studying flatworms have also described ruptosis, in which particular cells explode and spread toxins against invading bacteria. Such findings suggest that cell death is not a single general-purpose process. Different cells may have specialised ways to sacrifice themselves, depending on their location and role.
Why the route to death matters
Billions of cells die in the human body each day as damaged, worn-out or unnecessary cells are removed. This can support normal development and tissue maintenance. During embryonic development, for example, apoptosis removes cells that create the temporary webbing between developing fingers. Some intestinal cells have limited lifespans, while certain skin cells die through cornification and leave behind a protective outer layer.
Cell death can also be part of the immune response. An infected cell may destroy itself to limit a virus or bacterium, while releasing signals that recruit immune cells. Some dying immune cells perform additional tasks before they disappear. A bacterium-infected macrophage can die through pyroptosis while arranging its membranes to trap pathogens in its remains. Neutrophils can release webs made from their own DNA to ensnare bacteria as they burst.
This has led to the idea that cells may have a “bucket list” of tasks to complete before death. The concept is attractive because it explains why some cells appear to remain functional during the early stages of a lethal process, but it is difficult to test experimentally.
Cells can also delay death or, in some circumstances, recover. In experiments involving mice infected with Salmonella, intestinal cells lacking the enzyme caspase-7 began to die but remained in the gut lining instead of exiting. Their damaged membranes developed holes, contributing to inflammation and tissue injury. Caspase-7 normally helps repair those holes, allowing a dying cell to survive long enough to leave the tissue cleanly.
Another process, called anastasis, was observed when researchers removed a chemical that had triggered apoptosis and placed struggling cells in fresh culture medium. Many of the cells recovered after activating repair pathways. Reversal has since also been observed after ferroptosis and necroptosis.
The findings shift the question from simply asking whether a cell is alive or dead to asking where it is along a changing process. Researchers suspect that an irreversible point may arrive when the boundaries of the mitochondria—the structures that support cellular energy metabolism—are permanently disrupted. That remains a working idea rather than a settled rule.
The medical interest lies in controlling the route. A treatment might be designed to push cancer cells into a vulnerable death pathway, interrupt a pathway that drives damaging inflammation, or help injured cells survive. These applications are still areas of research, but the growing number of pathways gives scientists more biological mechanisms to investigate.