People who have a diagnosis of cancer and are undergoing its treatment have a greater risk of infection. Over the years, several scientific studies have indicated that there is a definite link between cancer and the immune system. When your body is fighting cancer, your body’s defense mechanisms experience significant changes. This link between cancer and a higher risk of infection has several underlying causes. Cancer itself leads to a higher chance of infection. Besides, ongoing treatment may also raise its risk. Sometimes, you may fall prey to infection because of your medications or poor nutrition. To understand why this happens, it is important to understand the role of the immune system.
How the Immune System Protects from Infection
Your body is equipped with several mechanisms that protect against disease and infection. The skin acts as a barrier and forms the first line of defense for the internal tissues. Mucous membranes are found in the mouth, throat, eyelids, and digestive tract lining. These membranes provide a partial barrier against infection originating from the air, food consumed, or the environment.
When the immune system function is optimal, it protects the cells, tissues, and organs against infections. The main types of infection-fighting cells are neutrophils, a type of white blood cells. Other forms of cells include monocytes, macrophages, and lymphocytes.
How Cancer Affects the Immune Function
Certain cancer types such as Hodgkin’s lymphoma and leukemia modify the function of the immune system. These types of cancers start in the immune system cells. Other forms of cancer also change the immune system, causing it to lose its protective effect. Cancer can also invade the bone marrow and destroy cells. This happens when cancer cells compete with bone marrow cells for nutrients and space. Reduced cells in the bone marrow cause an inability to produce enough white blood cells. Eventually, your ability to fight infection is affected.
Skin cancers tend to break the natural barriers and allow germs to enter the system. Large tumors reduce blood supply to normal tissues. Tumors that grow in the lungs block the drainage of the mucous and lead to all types of infections. Tissues that have been damaged by cancer may also be susceptible to infection.
Cancer Treatment and the Immune Function
Chemotherapy, radiation therapy, immunotherapy, surgery, or the use of catheters damages the mucous membranes and the skin. This causes pathogens to easily attack the human system. Cancer treatment can have a damaging effect on the immune system in the short term as well as the long term. Radiation therapy or chemotherapy typically causes immune system damage in the short term.
An invasive treatment such as one that involves the surgical removal of the spleen causes long-term damage. This is because the spleen participates in the healthy functioning of the immune system. Surgery performed for cancer involves the use of drugs and anesthesia, which affect the immune system. Besides, the surgical procedure itself can attenuate the immune response considerably.
Finally, recovery from cancer treatments increases the need for nutrients. Cancer and its treatment may deplete the body with essential nutrients. A lack of nutrients also contributes to infection susceptibility.
Cancer Treatment and Immune Function Disruption in Detail
The nature of therapy administered for cancer is closely associated with how it affects your immune system. Chemotherapy drugs are designed to target fast-growing cells. Although cancer cells are a type of fast-growing cells, some other cells like those present in the bone marrow are also fast-growing cells. When chemotherapy drugs target these cells, the production of immune cells is disrupted. This disruption, in turn, renders you more vulnerable to diseases and pathogens.
Surgery restores the function of the immune system after the removal of the tumor. But a major surgery can overburden the immune system. Surgery weakens the immune system, making it incapable of protecting the body against infection. The surgical procedure severs the skin and tissues and opens up different protective layers to infection. Sometimes, surgical removal of the lymph nodes may be required. Lymph node removal further reduces the system’s capacity to fight infection.
Immunotherapy drugs assist the immune system in recognizing and attacking cancer cells. However, when an immune system is overactive, it may attack even healthy cells. This causes auto-immune conditions such as colitis or flu-like symptoms.
Radiation therapy destroys cancer cells along with healthy cells, leading to an increased risk of infection. Cancer types such as lymphoma and leukemia are treated using CAR T-cell therapy. T-cell therapy uses re-engineered immune system cells to attack cancer cells. The downside of this therapy is that it damages or depletes B-cells. A low B-cell count leads to the body’s inability to produce antibodies.
In stem cell transplants, healthy cells replace immune system cells. Stem cells are harvested from the body of the patient or a different donor. In some cases when the stem cells are taken from a donor, the body of the recipient may reject the cells of the donor. This may cause infections to occur more frequently.
Cancer and Blood Cells
Treatments targeted at cancer cause multiple types of conditions. These conditions lower the volume of different constituents of the human blood. The patient may suffer from thrombocytopenia or an abnormally low platelet count. This condition may occur in response to a viral infection.
Further, when cancer treatment causes low white blood cell count, it results in a condition called leukopenia. Leukopenia also makes your body more susceptible to infection.
Another condition that may occur after cancer treatment is neutropenia. Neutropenia relates to a decrease in the neutrophils in the blood. In some cases, the red blood cells, white blood cells, and platelets may fall below the required level. This decline may cause anemia and excessive bleeding, while also making your body more susceptible to infection.
Tumors, Immunomodulation, and Immunotherapy
Research evidence indicates that cancer can be the cause of disruption throughout the body. This means that several systems may be affected beyond the primary site of the location of the tumor. Understanding the nature of immune system disruption helps to improve immunotherapy outcomes. Cancer affects the immune system systemically. This means that immunotherapies must have a long-lasting effect to be able to modulate the immune response in a positive manner. Cancer, when left untreated, changes the immune response. This can happen locally as well as at a distance from the tumor.
Furthermore, in cancer, immune system disruption tends to evolve over the course of the disease. However, it is possible to reverse these disruptions when the tumor is removed surgically. Immune system types and cells are also affected differently depending on the type of cancer invading an organism. This relates to the differences in the physiology of different tissues. The immune system, which is compromised by cancer or its treatment, is unable to set up an immune defense. This results in an exacerbation of cancer as well as an inability to fight infection.
Immunotherapy Outcomes in Cancer
The outcome of immunotherapy depends on how far the cancer invasion has weakened the immune system. When a person’s immune system can mount an immune response even when affected by cancer, there is a greater chance of the success of immunotherapy.
However, the real challenge lies in being able to maintain the required immune cells systemically. Precisely, the growth of tumors is associated with a reduction in the activation of the antigen-presenting cells. These antigen-presenting cells act as precursors for T-cell activation. Research indicates that the function of the antigen-presenting cells may be altered in a state of cancer. Therefore, reduced antigen-presenting cells and T-cell activation lead to an altered immune response.
The major role of immunotherapy is to stimulate these immune system cells. The degree of success of immunotherapy relates to how far it can stimulate immune cells. When the therapy is successful, killer “T” cells can eventually set up an attack against the cancer cells.
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