For the first time, scientists have watched a killer cell attack a tumor cell in three dimensions. The images, published on 29 April 2026 in Cell Reports, show how immune cells destroy cancer at the nanometer scale.
The research comes from the University of Geneva and Lausanne University Hospital. These Swiss institutions used a new technique called cryo-expansion microscopy, or cryo-ExM. This method flash-freezes cells so quickly that water becomes glass-like, preserving biological structures perfectly. Then, the frozen samples are placed in a special gel that stretches them, allowing ordinary microscopes to see tiny details.
The team captured cytotoxic T lymphocytes, the white blood cells that kill cancer, in action. At the point of contact, they found something striking: the cell's membrane forms a dome-like structure. Inside this dome lie tiny packages called cytotoxic granules, which contain killing molecules including perforin and granzyme B.
The researchers did not stop with cells in a dish. They studied the technique in human tumor tissues, observing T lymphocytes directly attacking cancer cells. This matters because immuno-oncology treatments, which use a patient's own immune system against cancer, work for some patients but fail for others. Scientists do not fully understand why.
The Swiss team argues that their framework helps explain when immune responses succeed and when they fail, which should guide the design of better future therapies. For the first time, we can see exactly how a killer cell destroys cancer.