es it is very true. Currently the science has an understanding of this fact but not the complete details of it. Nature has made our immune system good enough to fight every offending agent and its product so that they do not harm the body. Be it the infection or cancer. There is a balance between genetic environment, immune environment and the offending agent which can be internal or external. This balance can be upset by the increase or decrease of any of the factors. It is something like war between armies. So if the offending agent is very strong, the other systems can be overrun. Also if the immune system or genetic system is weak then the offending agent can get through and cause cancer. Some times, the cancer cells evade the immunity through ‘fooling’ the system by several mechanisms.
So understandably, only when the balance is upset and system fails the result is an infection or cancer. For example, many people are exposed to the same ‘cancer causing agent’ (carcinogen) in the same manner for the same duration. But everyone does not get the cancer and only few get it.
Science is beginning to understand this marvellous mechanism in our body. There are many ways this system works. This is operative through antibodies, cytokines or cytotoxins (some kind of toxins chemicals) secreted by immune cells, cancer killing T cells, activation of other immune cells, modification of the cell environment to name some.
Under normal conditions, the immune system performs a series of steps which lead to an anticancer immune response and cancer cell death, known as the cancer immunity cycle. The steps are
Tumor cells produce mutated antigens that are captured by dendritic cells.
The dendritic cells prime T cell with tumor antigen and stimulate the activation of cytotoxic T cells (killer cells)
Activated T cells then travel to the tumor and infiltrate the tumor environment.
The activated T cells recognize and bind to the cancer cells.
The bound effector T cells release cytotoxins, which induce death (apoptosis) in their target cancer cells.
But when this mechanism fails due to some reason, cancer can happen. Current immunotherapy of cancer is addressing this aspect of science.
To conclude nature has made a beautiful defence system in our body to fight many things including cancer and when this system fails – cancer is the result!!