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Humans are born with an immune system, which is necessary to support life. This system is maintained by the activities of immune cells. There are many types of immune cells with various roles. All the immune cells cooperate in constantly protecting our bodies from the invasion of outside enemies or the threat of cancer cells.
Immune cells are present in white blood cells in blood.
When we roughly classify immune cells by their roles, first, there are “granulocytes” which instantaneously protect our bodies from bacteria or other infections. Pus that appears in injuries or infection comprises dead granulocytes, which fights bacteria.
There are “lymphocytes” that serve as patrolling police officers or soldiers. They monitor for abnormal cells (cells that are enemies of our bodies) and destroy them every day.
“T cells” account for about 70% of the lymphocytes, followed by “B cells” that produce antibodies and “NK (natural killer) cells” that form an elite troop that destroys abnormal cells without mercy, each accounting for 10%.
Moreover, it is known that there are only a few percentages of NKT cells and γδT cells that target and damage cancer cells.
There is still another type of lymphocytes, “monocytes”. Monocytes pop out of blood vessels, become ameboid “macrophages”, take foreign objects such as bacteria into themselves, digest them and present their parts on their surface (antigen presentation). Macrophages play the role of an educator/commander along with “dendritic cells” that have more functions than macrophages. Macrophages tell T cells that act like soldiers the presence of abnormal cells including cancer and educate them about the fact that these abnormal cells are enemies.
Lymphocytes are involved in 2 types of immunity—one is “natural immunity,” in which lymphocytes respond to the invasion of pathogens such as virus within 4 hours, and the other is “adaptive immunity,” in which they need a few days to respond. NK cells, NKT cells and γδT cells function in natural immunity and T cells function in adaptive immunity.
A representative example of adaptive immunity is vaccination with pathogens such as a measles virus. In vaccination with a measles virus, a very small amount of T cells that respond only to this virus and B cells that produce antibodies are induced and extensively proliferated, creating the system for fighting a measles virus. Some T cells remain in the body for a long time as memory T cells. After vaccination, when the body is infected with a measles virus, these memory T cells quickly respond and are greatly increased, thereby protecting the body from infection with a measles virus. This function of T cells is called adaptive immunity.
It takes a while for T cells to establish such a one-on-one relationship, in which they respond only to specific enemies.
On the other hand, when NK cells representing the cells involved in natural immunity encounter the cells that are enemies of the body, such as cells infected with virus or cancer cells, they attack these enemies immediately. This is an important natural function of NK cells.
Thus, our health is maintained when our immune system is in good condition and functions properly, and its 2 forms, natural immunity and adaptive immunity, complement each other.
The human body is made up of about 60 trillion cells. It grows and survives through the renewal of these cells that continues every day. In the process of the renewal of cells, about 5000 sprouts of cancer cells are thought to be created daily in adult cases. These sprouts do not immediately develop into cancer. Some people do not have cancer all their lives. This is thought to be mainly because of the function of immune cells.
A type of lymphocyte, NK cells patrol throughout the body, find the sprouts of cancer cells and immediately eliminate them ruthlessly. NK cells in healthy people work very well, attacking the sprouts of cancer cells while they are being generated left and right. The sprouts of cancer cells broken into pieces in the initial attack are processed (phagocytosed) by the educators of cells, called dendritic cells, which instruct T cells to “eliminate abnormal cells like these if they are found”. When T cells receive this information, they rapidly increase their soldiers that can attack the same kind of cells as those presented by repeating cell division, thereby building up the power to attack the abnormal cells of the same pattern immediately after they are found. In a healthy body, different cells share tasks and play their roles to maintain a strong defense system.
What is important here is the role of NK cells, the initial responders. Such a coordinated system works only when NK cells diligently patrol the body and successfully perform the initial attack, that is, they eliminate strange cells immediately after finding them. However, these NK cells are affected by aging or stress very easily. Sometimes, they are reduced in number or their attacking capability becomes extremely weak, which makes them unable to play the role as the initial responders at all. When the power of NK cells is weakened, unprocessed abnormal cells remain and accumulate. This is a major factor that triggers development of cancer.
When NK cells become weaker and sprouts of cancer cells tend to remain, dendritic cells (educator/commander) try hard to prevent cancer by educating T cells and strengthening the troop. This period—during which dendritic cells are trying hard and the offense by cancer cells and the defense by immunity are barely balanced—is thought to last for 5 to 10 years, depending on the individuals. The cancer cells that survived through this period gradually develop resistance to immunity and quietly continue to grow.
And at one point, the attack capability of either NK cells or T cells becomes insufficient. Cancer cells suddenly start to proliferate rapidly. This is when shadows suspected to indicate cancer start to appear in CT images. The cancer lesion grown to the size of 1 cm has about one billion cancer cells. At this point, cancer cells surround themselves with a defensive barrier that is resistant to the immunity (or inhibit immunity) produced in various methods and proliferate even more.
When people are diagnosed with cancer, the momentum of cancer is very strong, while immunity is greatly weakened. The power relationship is completely opposite compared with that in healthy condition. Thus, cancer treatment is usually started after the conditions changed in this way.
As immunity is weakened and cancer cells are strengthened in the mechanism of cancer development, it is effective to reverse the process in cancer treatment. Cancer cells have gained momentum, being protected from immunity by a solid barrier and immunity has been weakened. It is essential to first solve this imbalance and restore the past condition in which malignant transformation and immunity were barely balanced.
One way of doing so is to use standard therapies such as anticancer agents, radiation, and surgeries to weaken the power of cancer cells that have gained momentum and to regain the condition in which immunity was able to control the cancer cells. By weakening the power of cancer cells themselves, the immune system resumes producing effects. In particular, it is considered that anticancer agents lower or partially destroy the defensive barrier, making it easier for immune cells to get over the barrier and enhancing their capacity to attack.
However, anticancer agents generally target the cells with a high proliferation rate. Therefore, at the same time that these agents destroy cancer cells, they greatly impair the growth of the parts of the body where normal cells divide rapidly, such as bone marrow, liver, kidney, mucous membranes, hair roots, nails and skin. Immune cells produced in bone marrow are not the exception. Their functions are inhibited and therefore, immunity is weakened.
What is important in cancer treatment is to prevent further weakening of already weakened immunity and to enhance it.
Before explaining the method to strengthen immunity, let’s review the causes that are already known for the weakening of immunity and its inability to contain cancer cells.
In order to enhance immunity, we just have to try to lead a life without these causative factors.
Even though we cannot avoid aging, we should try to maintain age-appropriate or stronger immunity by improving our daily lifestyle.
Furthermore, immunotherapy is very effective as an ultimate method to enhance immunity. In particular, it is essential to increase “NK (natural killer) cells”, the troop that initially attack sprouts of cancer cells ruthlessly, and enhance their ability (activate) in order to build a body that is not easily affected by cancer.
We cannot feel relieved even if a cancer lesion was removed by surgery, or if the size of the tumor was reduced by radiation therapy or anticancer agents, making shadows on CT image undetectable. This is a troublesome aspect of cancer.
Cancer cells that went into the blood during surgery can remain in the body and cancer cells that were thought to have disappeared can resume growth for some reasons. In order to prevent recurrence, it is important to build up the power in your body to attack such potential cancer cells. A lifestyle that enhances immunity is desirable in order to maintain the power in immunity that makes it possible for immune cells to constantly function dominantly. At the same time, it is also effective to periodically check immunity and supplement it in order to prevent recurrence.