There are lots of things in life we take for granted. One of these things is our immune system. Without it, we literally would not be here. Our immune systems fight off disease and infection daily whether we are aware of it or not. Sure, we learn about it in school, but how much do really know about it?
The immune system is often overlooked but should still be understood. Not only historically, but what it can aid in our futures. From cancer to vaccines, this remarkable system offers us much more information than we realise.
In this book summary readers will discover:
- The three types of immune responses
- The three laws of immunity
- The dark side of immunity
- How the immune system can potentially fight cancer
Key lesson one: The three types of immune responses
The immune system is as complex as they come. It fights potential threats on three fronts. The first of these is in the form of a physical barrier. Our mouth and noses are lined with mucus which acts as a physical barrier that traps bacteria before it can further harm our body. This bacteria containing mucus is then either swallowed and destroyed by stomach acid or removed from the body when we blow our nose or spit it out.
The second type of immunity is innate immunity. This is whereby particular cells detect dangerous bacteria and begin to attack them. In this response, all cells have the same capacity to seek and destroy the bacterial pathogen. The last type of immunity is called adaptive immunity. This response differs from innate immunity because specialized cells are produced to fight the specific threat. After the body recovers, some of these specialized cells remain to protect against future attacks.
These three immune responses are what protects us from infectious bacteria and viruses that aim to harm us.
Key lesson two: The three laws of immunity
Regarding the three types of immune responses, there are three laws that govern immunity. They are the law of universality, the law of tolerance and the law of appropriateness.
Law one – The Law of universality
The law of universality basically states that specialized antibodies can be produced by the immune system for any threat. This law has been talked about since the early twentieth century with the biggest question being how can the immune system have such specificity? How does it know which antibodies to produce?
The explanation began in 1901 when Paul Ehrlich, a German scientist, first proposed that antibodies attracted antigens by being similar to the cells they would normally target. The antigens would head towards the antibodies thinking they were other cells and would then be attacked by the antibodies. This prevented the antigens from actually reaching the cells they wanted to infect. The flaw in Ehrlich’s theory was that he believes that antigens were quite limited. This was disproved later on when it was discovered that any chemical compound with a protein could be considered an antigen.
Almost five decades later, David Talmage and Frank Macfarlane Burnet based their theory of specificity on lymphocytes. Lymphocytes are the white blood cells that are integral to adaptive immunity responses. Their theory suggested that lymphocytes had different receptors that recognized specific antigens. Thereby when a specific antigen makes an appearance in the body, it is identified by specific lymphocytes and specific antibodies produced as a response. This theory is now known as clonal selection and is accepted by the scientific and medical communities. It is this theory that sits behind the law of universality.
Law two – The Law of tolerance
The law of tolerance simply states that the immune system will not attack the cells of its host. It’s all about preventing harm to the body by its own defence system. So, what stops our immune system from attacking us?
Immune systems can be defective and attack our bodies – many auto-immune diseases exist. But under normal circumstances, the immune system prevents this from happening by sending very specific cells to stop any self attacks. These cells are known as regulatory T-cells. As the name states, they’re in charge of regulating T-cells which are sent out to destroy cells infected with viruses. If the immune system does not produce regulatory T-cells, autoimmune responses will occur which put the host in danger. This is not only a problem in humans as it has also been seen in rats. Thus, rats are commonly used in experiments regarding immune responses and regulatory T-cells.
Without regulatory T-cells, T-cells would never be controlled and our immune system would attack our own healthy cells. Therefore the law of tolerance is only applicable in a healthy immune system where regulatory T-cells are functional.
Law three – The Law of appropriateness
The law of appropriateness states that every pathogen needs a very specific immune response. Pathogens exist almost everywhere and it often seems like they are just waiting for a chance to infect a healthy body. Some are quick to cause disease and destruction while others take a more subtle route, entering cells and slowly changing them to something else entirely. So, how does the body produce a specific immune response to fight off very different pathogens?
Once again, it is the T-cells that provide the answer. In general, an immune response depends on having the appropriate T-cells to kill a specific pathogen. This was proven by Richard Locksley when he studied mice infected with a specific parasite called Leishmania major. His study showed that some of the mice were able to get the infection under control while others could not. The difference in immunity between the mice all came down to the strength of the dendritic cells present. Dendritic cells are specialized cells that identify and interpret threats in the body. These are the cells that call upon specific T-cells once they recognize a pathogen. Whilst regulatory T-cells prevent T-cells from destroying the body, dendritic cells act as the alarm system which orders the right T-cells to be activated.
This allows the appropriate cells to be called into action to fight off a pathogen and is the foundation of the law of appropriateness.
Key lesson three: The dark side of immunity
As remarkable as the immune system is, it also possesses a dark side. If it has a slight flaw and works a little different to normal, it can attack your body instead of protecting it. In order for the immune system to function properly, the body itself must strike a fine balance.
To explain this further, consider the example offered by diabetes. The immune system of people who have Type 1 diabetes attacks its own body. T-calls, whose normal function is to kill viruses in the body, start attacking the body’s insulin-producing cells. As these cells are crucial for regulating blood-sugar levels, their destruction leads to diabetes.
This is just one example. A malfunctioning immune system can cause a multitude of problems. It is extremely hard for individuals who have to fight the system that was meant to protect them in the first place.
Key lesson four: How the immune system can potentially fight cancer
Cancer still remains one of the main focuses of medical research. The disease has had scientists and doctors baffled as their every attempt to fight it has not succeeded in curing it. Now, they have turned their focus to the immune system as an ally to the fight.
This stems from the fact that building immunity can actually slow the growth of tumours. In Taiwan, the hepatitis – B vaccine was shown to reduce the occurrence of cancer of the liver. They compared the rates of liver cancer to those born before the implementation of the vaccine to the rates of those who received the vaccine a decade later. An 84 per cent decrease in cancer of the liver was discovered. So, how does a vaccine help in the fight against liver cancer? Well, the most likely answer is that the immune response that occurred in response to the vaccination reduced the risk of cancer.
The results of the investigation in Taiwan was not a once-off. Previously, a study in Seattle in the 1950s also showed that immunity could fight off tumours. More specifically, this study found that tumours contain antigens that could be fought off if the immune system produced the correct antibodies. They exposed mice to a cancer-inducing chemical and when the tumours grew to a specific size they were surgically removed. After a few days, the tumours were implanted back in the mice along with new mice that did not have cancer. Out of the non-cancerous mice, 83 per cent of them exhibited tumour growth. In contrast, the cancerous mice from which the tumours were removed all rejected the tumours. This implied that they had developed some immunity to this type of tumour.
It is these studies that have given scientists and doctors the idea of using immunity against cancer. However, it is still a long journey as cancer research is a long and winding road that still being discovered.
The key takeaway from Immunity is:
The immune system is often taken for granted. It plays a role in keeping us safe from infection daily. One small flaw in our immune system results in many problems which could potentially make it a threat. However, understanding how immune responses work and the laws that govern them is important in understanding the role immunity has in medical research. As much as we have learned much, there are still many avenues to explore to see just how the immune system can aid in the fight against diseases like cancer.
How can I implement the lessons learned in Immunity:
Your immune system is always hard at work but there are simple steps you can take to also help it out. Always practice good hygiene to prevent pathogens from entering your body or being spread to others if you are sick. Wash fruit and vegetables before preparing them and always make sure surfaces are clean before handling and cutting proteins like chicken, meat and fish. A healthy diet together with daily exercise will also help boost your immunity.
