In recent years, immuno-oncology has received a lot of hype and praise because of some high-profile success cases, such as former president Jimmy Carter, and investments from popular culture icons like Sean Parker. What makes immunotherapy such an exciting option for the field of oncology is that it bolsters the body’s natural immunity to disease.
Our bodies already contain the tools necessary for fighting and beating cancer, but the disease can develop ways of bypassing the immune system and tricking it so that it leaves tumors unharmed. A major aim of immunotherapy is removing these bypasses so that the immune system can attack cancer cells and destroy them without the use of toxic treatments like radiation and chemotherapy.
To understand what immuno-oncologists are working toward, it is important to comprehend how the immune system works and how it can eliminate tumors.
An Overview of Innate Immunity
The body’s immune system is divided into two components, the most basic of which is called innate immunity. In many ways, innate immunity is the body’s first line of defense that acts immediately to defend against infection from foreign invaders. The innate immune system includes everything from the skin that protects our internal organs to neutrophils—white blood cells that seek out and kill infectious organisms. While the innate immune system does not
play a direct role in fighting cancer, it is still important for keeping the body healthy so that other parts of the immune system can focus on tumors rather than other infections.
Cancer can inhibit the immune system in many ways, especially through traditional treatments. For example, chemotherapy damages the lining of the gut, which produces mucus that traps invading bacteria. Radiotherapy can damage mucus cells, too, as well as the hair cells that help remove the bacteria that become trapped in mucus. Also, IV lines in the arm break the skin barrier and provide another route for bacteria’s entry into the body, as do catheters.
One of the biggest issues associated with cancer treatment and innate immunity is the fact that chemotherapy and radiotherapy can reduce the neutrophil count in the blood stream, which inhibits the body’s ability to ward off infection. Neutrophils normally travel around the blood stream and adhere to bacteria, viruses, and fungi and then either digest these invaders or chemically kill them. With a reduced number of neutrophils, people are more susceptible to infections, which can quickly become very serious. Individuals regularly carry bacteria in their bodies that are kept at bay by neutrophils, but these can begin to spread when the neutrophil count drops. This type of infection can prove fatal if doctors don’t immediately administer antibiotics.
The Importance of Acquired Immunity in Fighting Cancer
The other part of the immune system is called acquired immunity because it develops over time as they body encounters various diseases. As the immune system learns to recognize specific bacteria and fungi, it can more effectively fight them off in the future. The acquired immune system is the reason that people usually only get diseases like chicken pox and measles once in their lives. Vaccinations are meant to expose the immune system to certain diseases artificially so that it can recognize and dispose of them quickly in the future.
Lymphocytes are the primary agents of acquired immunity. The main lymphocytic cells include B cells and T cells, which are white blood cells that are made in the bone marrow. B cells are responsible for making proteins called antibodies. Each antibody is specific to a different foreign body, including cancer cells. Antibodies bind to the surface of invaders, thereby marking the cells and signaling to the body that the cells need to be killed. Antibodies also detect damaged cells and identify them for destruction. B cells act as the memory system of immunity. When the same invader reenters the body, B cells can produce the relevant antibody very quickly. Each B cell makes a specific antibody capable of recognizing a certain bodily invader.
T cells mediate the acquired immune response to pathogens. Two different types of T cells exist: helper T cells and killer T cells. The helper T cells stimulate B cells to make antibodies that mark foreign invaders once they are detected. Then, killer T cells execute the marked cells. Often, killer T cells kill the body’s own cells once they are infected by a bacteria or virus. These cells are killed to prevent the invaders from reproducing and infecting surrounding cells. Each day, killer T cells can destroy thousands of infected cells, including cancer cells.
Some other important elements of the acquired immune system include cytokines, which help immune cells communicate and coordinate a response, and dendritic cells, which digest invader cells and present distinguishing proteins to immune cells so that the immune system can recognize them. The acquired immune system also has regulatory T cells that provide a sort of “checks-and-balances” process to prevent an immune overreaction.