What is Immuno-Oncology?
The immune system is a collection of molecules in every living thing that protects its cells. It relies on the ability to tell the difference between its own body cells and foreign cells, called antigens, in order to protect the body from the harmful antigens. The immune system has a set of proteins commonly referred to as MHC that “mark” which cells are foreign antigens and which cells are native to the host. After the two sets of cells are marked, the immune system kills the antigens to keep the host cells healthy.
Some of the most important cells for the immune system are produced by a subsection of it: the lymphatic system. This system is composed of the spleen, bone marrow, and the thymus. These produce white blood cells and other cells that fight antigens in addition to creating compartments for those cells to fight the antigens.The different cells are specialized so they can provide different antigen fighting functions for the host.
Bone marrow produces two different kinds of stem cells. The first is the most basic kind of immunity for body defense, while the second are more specialized to fight more aggressive disease. The main function of the first kind is to use receptors on the cells to identify the foreign cells that need to be compartmentalized and killed. The second type is responsible for “cell memory”, so the immune system can build up resistance to different antigens and gain immunity over time.
There also two different types of cells called T-cells that fight infection and disease. The first kind release cytotoxins, which are cells that are poisonous to infected cells thereby eliminating them. The second kind enhance the immune systems ability to find the infected cells, making those cells either to mark and kill. B-cells also help fight the infected cells, and they are slightly more effective than T-cells because T-cells require a protein to be able to identify infected cells, while B-cells have their own receptors to identify antigens that need to be killed. It is the combined action of these systems and cells that help the healthy host fight against infected cells.
Immune System and Cancer
Any impairment of the immune system produces disorders in the host, including autoimmune diseases where the immune system cannot tell the difference between host cells and foreign antigens. One of these is cancer. The immune system has three processes for fighting cancer: elimination, equilibrium, and escape.
In elimination, the cells that are most likely to turn into tumor cells are surveilled by the immune system. Once they do turn into tumor cells, they send antigens into the bloodstream. The cells needed to fight this antigen are then recruited from the lymphatic system. Of these the most important are called “Natural Killer” cells, and they are most important because they play a pivotal role in the recognition of the antigens and release the toxins most harmful to infected cells.
In equilibrium, tumor cells that evade elimination grow for a period up to a few years, and the ones most resistant to the immune system eventually develop into a tumor. Escape follows, where the full tumor continues to grow and produce cancer among other harmful effects.
The tumor cells can fool the immune system by mimicking normally produced proteins so these cells don’t get marked and the immune system does not attack them. They can also survive by releasing toxins that hurt the natural killer cells.
The problem with treating the infected cancer cells is that all treatments also injure healthy host cells, which has harsh effects on the patient’s overall health. Scientists are currently developing a different treatment method, where the cells in your immune system are cultured artificially and made stronger than normal in order to combat cancer without killing host cells.
Treatments can be separated into passive immunotherapy and active immunotherapy. Active immunotherapy either utilizes the patient’s own cells to fight the cancer by further stimulating the immune system, or uses what is called a vector basedmethod, where tumor specific antigens are injected into the host after being infused with immune cells.
Passive immunotherapy uses antibodies, cells that fight disease, that have been produced in a laboratory and are designed to fight proteins associated with cancer by attaching to the infected cells. After attaching, they engulf the infected cell membrane and eventually it is destroyed. Another avenue for the antibodies is to bind to the receptors that cancer uses to attract proteins that it needs to survive. These infected cells then stop participating in the cell cycle and self destruct.