The underlying idea behind all mammal biology is that the body is a delicate and complex creature under attack by a variety of scary diseases and that the immune system is in charge of keeping it safe. Immune cells scour every tissue in the body in search of intruders like parasites, viruses or bacteria or of something having gone wrong, nipping potential cancer in the bud. Immune cells zip through the body through the complex system of veins, arteries and capillaries,freely slipping in and out of the blood stream to reach where they are needed. A site filled with immune cells responding to such an emergency will be filled with chemical signals indicating that this is the case – a very particular state known as inflammation. In many ways, they are like the police force. They receive distress calls from around the body where an injury might have occurred or where an infection might be developing and they rush to it to help. The distress call is usually transmitted by invisible chemical signals, which indicate to the immune cells where the emergency is as clearly as a radio call. Much like the police, immune cells are granted huge powers which they need to keep the body safe.
Immune cells constantly look for specific molecules on the surface of all other cells which their encounter. These molecules are known as antigens and act as a flag, indicating that the cell is healthy and currently engaged in legitimate activities. This process is, if you will, the cellular equivalent of a routine stop-and-frisk search. Cancer cells have evolved mechanisms to hide their malignant nature during these searches, as detailed in my previous post. Immune cells also have the power to kill cells that are sick and potentially dangerous for the organism and can recruit other immune cells to the site of infection, in the cellular equivalent of a policeman getting backup. Much like in real life, while these powers are essential for the functioning of society when used for good, they are incredibly dangerous if used for evil. One of the current frontiers in our understanding of how cancer operates is in regard to how cancer cells can get the immune system to help their growth and development.
In fact, one of the most dangerous stages of cancer development is the deliberate recruitment of immune cells and their manipulation into creating an inflammatory state that actually facilitates the growth and dispersion of cancer cells. Tumors have been shown to produce signals that are usually employed by immune cells to communicate with each other – jamming up the communication between different members of the immune system team and at the same time tuning them into dangerous pro-cancer machines. Immune cells manipulated in such a way can in turn produce more molecular signals that will help cancer cells hide, as well as encourage them to grow and move. This step is at the very forefront of a lot of the most interesting cancer research that is taking place at the moment all over the world. We don’t yet fully understand how cancer cells manage to turn the immune system against the organism and how to stop it, but e are making amazing progress in slowly unravelling each individual step cancer cells must go through in order to acquire this most dangerous ally.