Cytotoxic T Cells — sometimes called the cancer assassins — belong to our armies of white blood cells. They specialize in recognizing and eliminating cancer cells and cells infected with viruses. Once they identify their target cells, there is no going back, only forward — cytotoxic T cells are serial killers. They hunt down, attack and then eliminate cancer cells and cells infected with viruses, one after the other, tirelessly.
To kill their targets, cytotoxic T cells use a mechanism called polarized secretion. They inject highly toxic, lethal proteins known as cytotoxins into their target cells, and they do so precisely and selectively — their lethal injection system spares the healthy, neighboring bystanders cells.
Now, a research team has captured the process on film, using state-of-the-art imaging techniques. The film — produced using movies from a study published a few days ago in the journal Immunity — shows cytotoxic T lymphocytes as they hunt down and eliminate cancer cells before moving on to their next target. Team leader Gillian Griffiths said in a press release: “In our bodies, where cells are packed together, it’s essential that the T cell focuses the lethal hit on its target, otherwise it will cause collateral damage to neighboring, healthy cells. Once the cytotoxins are injected into the cancer cells, its fate is sealed and we can watch as it withers and dies. The T cell then moves on, hungry to find another victim.”
In the film (shown below), a cytotoxic T cell finds a cancer cell (blue). Membrane protrusions from the cytotoxic T cells rapidly explore the surface of the cancer cell, checking for tell-tale signs that this is an uninvited guest. The cytotoxic T cell binds to the cancer cell and injects into it poisonous proteins known as cytotoxins (red).