The Immune System and Cancer

Overview

Our body has an immune system in place to protect and heal itself. The immune system uses various mechanisms to defend the body from bacteria, viruses, and allergens, but it might not be the case when it comes to cancer. The uncontrolled division of the cancer cells hampers the active functioning of the immune system by manipulating it at a cellular level. There are emerging cancer therapies that can target the immune system and cause it to kill the cancer cells. It is believed that the immune system and cancer are constantly involved with each other. Understanding this involvement can help us gain more insight into how cancer progresses and affects the immune system and how new cancer treatments work on the immune system. 

This article aims to focus on the immune system, how cancer originates, and the connection between the immune system and cancer.

Understanding the immune system

The immune system is like in-built armour that is activated upon exposure to bacteria, viruses, parasites, chemical toxins, or allergens like dust. Collectively these agents are known as antigens. The Immune system recognises these antigens, infections, and damaged cells (even cancer cells at times) in the body and gives an immune response. 

The immune response can be divided, depending on the speed and mechanism of the reaction:^1,2

• Innate immunity: Innate or non-specific immunity is what one is born with and is known as the first line of defence in identifying and eliminating an antigen. This mechanism is always ready to protect the body against infections and quick to act against antigens. Innate immunity comes from many different physical and chemical barriers such as the skin, mucus, enzymes in tears, or stomach acid. Innate immunity also comes from white blood cells and a protein chemical called cytokine. If the antigens escape innate immunity, they will get eliminated by other parts of the immune system 
• Adaptive immunity: Adaptive or acquired immunity is obtained after the body is exposed to certain diseases. The immune system learns to recognize the different types of bacteria, viruses, and other antigens for decades due the memory cells such as T and B-cells. That is why diseases such as chickenpox and measles only occur once in a lifetime as our body remembers the virus that caused it and will destroy it if exposed again

To understand the immune system better, we need to know all the cells involved and their respective functions against antigens and cancer cells.

The cells involved with immunity and its responses are^2,3

• Phagocytes: a type of white blood cell that engulfs microorganisms and kills them. These cells are effective in eliminating foreign harmful substances, and dead and dying cells. The different types of phagocytes circulate the bloodstream and enter a tissue if it detects inflammation or infection. The cytokines secreted by these cells are responsible for the killing of the antigen causing the infection 

• Lymphocytes: also a type of white blood cell that remembers and recognizes antigens that previously attacked the body. Lymphocytes originate from the bone marrow and become B and T cells which are present in the bloodstream and lymphatic tissues

Understanding cancer

Cancer is the uncontrollable division of cells due to mutations in genes caused by exposure to harmful chemicals and radiation or through inheritance. Cancer is formed as tumours in various tissues, organs, blood, and bones. Cancer can spread throughout the body via the blood through a process called metastasis.⁴ 

Cancer symptoms depend on the type of cancer. Shortness of breath, for example, can be associated with lung cancer. But common symptoms such as unexplained weight loss, unhealed sore or new moles, lumps, and thickness of the skin in certain regions are seen in cancer patients.⁴ These symptoms can also be associated with other diseases so it is important that you reach out to your GP for guidance and support.

Commonly, men are more likely to develop lung, prostate, colorectal, stomach, and liver cancer than women, who are more likely to develop breast, colorectal, lung, cervical, and thyroid cancer.⁵ Cancer is commonly treated with chemotherapy, radiotherapy, surgery, and immunotherapy in recent years. The treatment is based on the diagnosis, stage of cancer, and how far it has spread.

Immune system and cancer, what is the connection?

Cancer is a disease that takes over your entire body including the immune system. The immune system has the capacity to distinguish healthy cells from cancer cells and can eradicate cancer cells before they even become a tumour. But these cancer cells can escape the immune system by preventing the infiltration of immune cells into the tumour microenvironment, and by escaping the immune recognition.⁶ The spread of cancer to the bone marrow and certain cancers such as leukaemia or lymphoma causes the bone marrow to produce fewer immune cells, hence weakening the immune system.⁷ 

Recent advancements in cancer therapy found a way to utilize the immune system in the killing of cancer cells known as immunotherapy. It aims to stimulate and boost the existing immune system to detect and destroy cancer cells. Researchers have also created chemical substances in labs to repair and enhance the immune system in cancer patients.^1,7 

The different types of immunotherapies are:^7,8

• Chimeric antigen receptor (CAR) T cell therapy: gene therapy to change the abnormalities in a person’s white blood cells

• Monoclonal antibodies (MABs): lab-made antibodies to mark cancer cell surface for the immune system to find and destroy it

• Cancer vaccines: aim to boost the immune system to destroy cancer cells

• Immunomodulators: drugs that enhance the immune system to respond to cancer cells

FAQs

How can I know if I have a weak immune system?

If you tend to get sick easily and take a longer time than usual to recover, you might have a weak immune system. Reach out to your GP to get appropriate tests done to find out more about your immunity.  

How do I know if I have cancer?

Symptoms such as abnormal lumps under the skin, unexplained weight loss, unhealed sores, and unexplained bleeding are some of the early signs. These symptoms might be caused due to other diseases, therefore immediately visit your GP for appropriate diagnosis and treatment.  

Can I still get cancer if my immune system is strong?

There is a possibility of preventing cancer if your immune system is strong. Having a strong immune system may also help to beat cancer quicker as you will respond better to immunotherapy.  

How do I boost my immune system?

Maintain a balanced diet, get plenty of physical activity, keep your weight in check, hydrate yourself, and get enough sleep.  

Summary

The immune system is an in-built protection system of the body against harmful and unknown substances. Cancer tends to affect the immune system and makes cancer patients prone to many infections. But luckily scientists have found a way to use our own immune system against cancer cells using immunotherapy. Immunotherapy only works on certain types of cancers. If you or anyone you know is diagnosed with cancer talk with your GP for support and treatment options.