This article takes a quick peek into the mechanisms responsible for immunotherapy’s success against cancer.
In our last article, we discussed the early beginnings of cancer immunotherapy and here, we explain how the concepts of immunosurveillance and immune tolerance, crucial aspects of immunotherapy, have contributed to understanding and treating cancer.
The origins of immunosurveillance date back to the early 1900’s when German physician Paul Ehrlich theorized that the immune system had mechanisms in place to protect itself against cancer cells. He believed that because of the defense mechanisms in place in people’s bodies, several cancerous tumors would be eradicated naturally. This theory was later expanded upon in the 1960’s when American physician Lewis Thomas and Nobel Laureate Frank M. Burnet hypothesized that the immune system destroys unwanted cells with white blood cells that acted like guards. It was only during the late 1980’s that the scientific community began to accept the idea that these very white blood cells destroyed cancer cells during experiments conducted by William Coley, the Father of modern immunotherapy, who injected inactive bacteria strains into cancer patients and noticed a reduction in their tumors.
But how was the immune system able to defend itself from cancer cells? The science behind immunosurveillance is straightforward yet effective nonetheless. It first recognizes tumor cells through their antigens, which are molecules present on the outside of a tumor cell but may not be present on a normal cell. The antigens can be present in several forms and vary based on various diseases. After the tumor cell is recognized, the immune system begins to release antigen-presenting cells(APCs) which, along with other helper cells, destroy cancer cells.
This begs the question – if the body is so effective at fighting off cancer cells, why do so many people die of cancer every year? Immunosurveillance isn’t perfect. Some cancer cells are able to escape the grasp of the immune system. The immune system is then fooled into believing that everything is well, when in reality, the tumor now starts to multiply until it is in such large numbers that the immune system can no longer fight back against it – a point known as immune tolerance.
While the immune system is a juggernaut that can handle a lot thrown at it, unfortunately, it cannot fight back against all pathogens and fails relatively frequently. That is why the use of other types of therapies such as monoclonal antibodies, are useful. This will be discussed further in the next article.