Please help me to understand immune checkpoints in an easy way to be able to explain it to lung cancer patients. Any videos, algorithm, or table would be helpful, too. —Name withheld on request

An important function of the immune system is its ability to distinguish between normal cells and cells that are foreign, such as a virus, bacteria, or cancer cell. This ability ensures that the immune system attacks the foreign cells, leaving the healthy cells to thrive. Immune checkpoints are the molecules that identify substances (proteins) that indicate the presence of foreign cells in the body.

When the immune checkpoints identify proteins from a foreign substance, it turns on (activates) the immune response to attack any cell with those proteins. Proteins from normal cells turn off (inactivate) the immune response. In this way, foreign cells are destroyed but healthy cells are not destroyed.

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However, cancer cells develop from normal cells that become altered and grow out of control and may not have proteins that activate the immune response. Immunotherapy manipulates the immune system response to identify cancer cells as foreign, thereby counteracting the cancer cells’ ability to hide from the immune system.

The video “Checkpoint Inhibitors: Taking the Brakes Off the Immune System” offers a simple explanation with animation of how these agents work. —The Editors


Cancer immunotherapy. American Cancer Society Web site. Accessed August 31, 2015.

Related video: Checkpoint Inhibitors: Taking the Brakes Off the Immune System