What is the immune system, exactly ?

The immune system, designed to keep the human body as protected and healthy as possible, consists of cells, tissues and organs that detect, control and kill organisms or cells that can trigger diseases[i].

These can be foreign pathogens, such as bacteria or viruses, or abnormal cells (think cancer cells) before they develop and become harmful.

When the human body is exposed to foreign or abnormal pathogens, the normal immune response presents as:

The immune system acts in two very distinct ways.

  1. Through innate or natural immunity

This is the immediate action, the body’s first line of defense against infection or disease. The reaction is quick but does not specifically target the attacking pathogen.

  1. Through adaptive or specific immunity

The response in this case is slower, but more targeted or specific. The immune response occurs when the body is exposed to certain pathogens or diseases, and while it does not occur immediately, it is increasingly tailored to the infectious agents in question. When confronted by a virus or bacteria, or in the presence of abnormal cells, the immune system generates antibodies that bind to the proteins on the surface of the abnormal cells. These proteins are called antigens, and their detection is what triggers immune defense mechanisms and prompts them to reject or destroy foreign or abnormal cells. This type of adaptive immune response prompts a parallel response called an immunological memory, which allows for a more rapid and forceful reaction if the same infectious agent is encountered at a later date.

The immune system agents with the most important role in the immune response are B lymphocytes (also called B cells) and T lymphocytes (or T cells); they work together to destroy abnormal pathogens or cancer cells. B lymphocytes produce specific antibodies while T lymphocytes have the ability to eradicate abnormal or cancer cells. These lymphocytes are produced in the bone marrow.

Despite this impressive defense system, cancer cells are wily and will sometimes successfully avoid being identified as abnormal cells. When this occurs, they can grow and spread without being hindered or destroyed by the body’s defense mechanisms.

Face off between the immune system and cancer cells

Numerous cancers are avoided thanks to the monitoring and destruction of abnormal cells by the immune system, all of it invisible to the human host. Cancer cells are a derivative of normal cells, in other words, cells that developed several anomalies when they multiplied and were ultimately transformed. Scientists know that this transformation process can have several causes but have yet to identify a common reason for this mutation.

When the process begins and remains unchecked by the body’s immune system, abnormal cells gradually morph into cancer cells. These transformed cells no longer fulfill their original functions and begin to develop their own defense, feeding and spreading mechanisms.

Cancer cells can thus develop a resistance to the body’s own immune system and devise ways of hiding. For example:

Different methods have, over the last several years, been developed to successfully “cure” cancer. Among the most notable of these are surgery, chemotherapy and radiotherapy.

Immunotherapy in oncology is not a substitute but rather, a complement for other treatments. Unlike the treatments that act on the growth and proliferation of cancer cells, immunotherapy in oncology affects natural anticancer immunity by stimulating its ability to eradicate cancer cells.

[i] These organisms or cells are called pathogens.