I Pity the Fool Who Infects Me!

What am I looking at?

This is a colored scanning electron microscopy image of a human killer T cell – also called a T lymphocyte, a CD8+ T cell, or a cytotoxic T cell (cytotoxic comes from the Greek words kytos, meaning “hollow,” like a cell, and toxikon, meaning “poison”).

Biology in the background

There are several types of T cells in the immune system, but the one pictured here is what is known as a killer T cell because it’s responsible for destroying cells in our bodies that have been infected with intracellular pathogens or that have become cancerous. These T cells recognize abnormal proteins on the surface of our own cells. These proteins act as a signal that the cell is infected with a pathogen or has mutated to become cancerous.

Once such a cell has been identified, the T cell binds to it and injects toxic chemicals into the cell to kill it. This prevents the spread of the pathogen to surrounding cells or, in the case of cancerous cells, prevents the metastasis of those cells to other parts of the body. Killer T cells can also attack foreign cells like bacteria directly, preventing the growth of the bacteria within the body.

Ironically, Mr. T, the actor known for his roles in TV’s The A-Team and the movie Rocky III (in which he uttered the famous line “I pity the fool”), survived T cell lymphoma – a cancer of the T cells. He once joked, “Can you imagine that? Cancer with my name on it – personalized cancer!”

In humans, T cells can reach about 10 micrometers in diameter, or roughly 7.5 times smaller than the width of a human hair.

Technique

This image was created using electron microscopy.