How Are Foreign Cells Destroyed

Published Date: 02 Nov 2017

Jasper Chow 8A

What is it?

The lymphatic system is a large network of lymph nodes, which are connected to each other via lymphatic vessels that circulate throughout the body. Firstly, when fluids pass through lymphatic capillaries (which are small blood vessels that have very thin walls that allow many materials like oxygen to pass through) lymph is formed. Lymph is usually comprised of excess fluid to be returned to our bloodstream and dead cells. After the lymph is filtered by passing through numerous lymph nodes, it eventually returns into our circulatory system after all the foreign substances have been removed by white blood cells. Lymph nodes are small glands in your body and they help you filter bacteria and cancer cells because they are filled with white blood cells, and white blood cells help fight off bacteria and viruses, and they remove the foreign cells from the lymph. When lymph nodes are swollen, it means the immune system is actually reacting to foreign cells or viruses inside your body, because more white blood cells will appear in lymph nodes that have been attacked by foreign invaders, making the node increase in size. Some lymph nodes you can feel are in your neck and your armpit; however, you can only feel these nodes when they are swollen. Organs that are important to the lymphatic system include the thymus and spleen. The thymus is an organ in your chest and above the heart and lungs. This organ produces white blood cells and releases them into the lymphatic system. The spleen is the largest organ in the lymphatic system and is located below the heart and on the left side of your abdomen. The spleen’s main function is to filter the blood and removes worn out or damaged red blood cells. In case you lose a lot of blood in an accident, the spleen stores some extra blood for you to use. Another organ is the tonsils, which contain white blood cells to destroy invaders. They are the red pulpy things on the inside of your throat. You may not be able to see it because most people have their tonsils removed.

Unlike the circulatory system, the lymphatic system does not have a "heart" to pump the lymph from one node to another. Instead, when you move, your muscles help the lymph move throughout the lymphatic vessels. That means, the more you move around (for example, while exercising) the more lymph flows through your lymphatic system, keeping you healthy because the foreign substances are destroyed in lymph nodes.

How are foreign cells destroyed?

B cells and T cells are commonly found in lymph nodes. Normally, they cannot identify antigens and foreign invaders. However, other cells that have the ability to ingest antigens and can break them up into fragments and attach them with an HLA molecule (human leukocyte antigen) can then proceed to attach the fragment to a T cell receptor (which is a special molecule on top of the T cell.) The T cell is now able to recognize the antigen and is able to attack the invaders.

What are memory cells?

After the foreign substances are removed, all of the white blood cells destroy themselves, with the exception of memory cells. Memory cells are preserved after the invaders have died, and they are left alive because your body has to remember how to fight them in case the same type of virus/bacteria invades again.

Why do vaccines/shots help us?

Vaccines/shots are actually viruses. However, these viruses are half dead and very weak. When your body reacts to the virus or bacteria, the immune system generates antibodies to kill the invader. Since antibodies can remember what occurred for a very long time, probably for the remainder of your life, if the real virus invades your body, your body can react to it more aggressively. On the other hand, though, sometimes your body will need to be reminded of how to kill an invader because your antibodies slowly die, or because the virus changes every year. This is why you need to take influenza shots every year, because they constantly change their genes, like from H1N5 (avian flu) to H1N1 (swine flu).

Why is it important?

The lymphatic system is important because with the fluids leaking out of blood capillaries, the lymph would swell if there were no lymphatic system to absorb it from the tissues.

About Cancer and Tumors

There are actually two types of tumors: benign ones and malignant ones. Benign tumors stay dormant in one place, but when they grow, they can still affect tissue growth, whereas malignant tumors will spread through your body through the lymphatic system and can usually cause death. Thus, doctors can check lymph nodes to see how much the tumor has spread through your body and determine the stage of cancer.

Major Lymph Vessels in the Lymphatic System

There are two main vessels, the right lymphatic duct, which takes lymph from the right side of the body, and returns the fluid into a vein in our neck. The other important vessel is the thoracic duct, derived from the word thorax. Thoraxes usually refer to insects, being one of the three parts of the body, the other two being the abdomen and head. In a human, the thorax is the area of our body between our chest and our neck. Therefore, the thoracic duct takes lymph from lower areas in our body, like our lower chest, and runs all the way up to our neck and returns the excess fluid in another vein on the other side of our neck.

Types of Diseases in the Lymphatic System

One of the diseases that cause problems in the lymphatic system is lymphadenopathy, which occurs when a lymph node swells up, the cause often being an infection. When the infection is cured, the swelling often returns to its normal state. On the other hand, if numerous lymph nodes are swollen, this may show you are affected by a more dangerous ailment. Lymphadenitis is similar to lymphadenopathy, but lymphadenitis is often caused by swollen tissue inside a lymph node, as a result of bacteria invading your body. Antibiotics are often very effective at curing your body of these bacteria. Splenomegaly is another word for "enlarged spleen." Normally, when you feel your abdomen, you can feel your rib cage, but not your spleen, since it is rather small. In the case of splenomegaly, your spleen can expand and grow larger until it is a few times bigger than what it was before, which could be an obstruction to your diaphragm. An obstruction to your diaphragm could cause pains to your shoulder and your spleen could burst, resulting in internal bleeding. Lastly, lymphoma is another disease that is similar to cancer. It happens when white blood cells are multiplying at an abnormal speed, possibly causing tumors to grow in that area.

How does it interact with other systems in the human body?

The lymphatic system interacts with many of the other systems in the human body, including the integumentary system, the digestive system, the muscular system and the circulatory/cardiovascular system. The integumentary system is a vital part of keeping things out of your body, because skin is a physical barrier against foreign and potentially harmful substances. When the skin secretes oils, it boosts your skin’s defensive ability. Furthermore, some immune cells live in the epidermis (the first layer of the skin) and can help defend the body from being attacked by malicious diseases. Secondly, the muscular system helps the lymphatic vessels to move lymph through the network of nodes, because skeletal muscles "squeeze" the lymph out of the tissue and help narrow the size of the lymph vessels, thus "squirting" the fluid back into the upper part of the human body. Thirdly, the lymph collected from tissue in the body flows through the many lymph nodes and lymph vessels while being filtered, but eventually empties into the veins in our neck and returns to our circulatory system. Finally, the digestive system and the lymphatic/immune system cooperate in order to protect the body from harmful pathogens (pathogens are invaders that have the ability to cause disease. They are often in the form of viruses or bacteria.) Your digestive tract, which consists of your mouth, esophagus, stomach and intestines, is very unprotected against pathogens since we all eat a lot, and many viruses and bacteria live in the food (for example: Certain types of beneficial bacteria live inside yoghurt.) Some antibodies live in your intestines and can support your digestive system by destroying pathogens there. Likewise, stomach acid can wipe out all of the bacteria and can therefore help the immune system.

Advances in Technology (Lymphatic System)

Article 1:

New imaging agent detects, maps cancers that have reached lymph nodes

Published on March 21, 2013

Drug designed and developed at UC San Diego School of Medicine

Researchers at the University of California, San Diego School of Medicine have shown that a new imaging dye, designed and developed at UC San Diego Moores Cancer Center, is an effective agent in detecting and mapping cancers that have reached the lymph nodes. The radioactive dye called Technetium Tc-99m tilmanocept, successfully identified cancerous lymph nodes and did a better job of marking cancers than the current standard dye. Results of the Phase III clinical trial published online today in the Annals of Surgical Oncology.

"Tilmanocept is a novel engineered radiopharmaceutical specifically designed for sentinel lymph node detection," said David R. Vera, PhD, the drug's inventor, who is a professor in the UCSD Department of Radiology. "The molecule, developed at UC San Diego School of Medicine, offers surgeons a new tool to accurately detect and stage melanoma and breast cancers while in the operating room."

On March 13, 2013, Tilmanocept received U.S. Food and Drug Administration (FDA) approval.

After a cancer diagnosis, surgeons want to be sure that the disease has not spread to a patient's lymph nodes, especially the sentinel nodes that may be the first place that a cancer reaches. The lymphatic system is a network of vessels and ducts that carry disease-fighting cells throughout the body, but can also act as a way for cancer cells to access the bloodstream. By surgically removing and examining the sentinel nodes that drain a tumor, doctors can better determine if a cancer has spread.

"Tilmanocept advances the molecular targeting in breast cancer. It's the first agent that is binding to a lymph node because it is a lymph node that plays an important role in metastasis," said Anne Wallace, MD, professor of surgery, UC San Diego School of Medicine and principal investigator of the study. "Tilmanocept's ability to identify more cancer containing nodes will lead to better post-operative care for patients, especially those patients who had more than one positive sentinel node."

Summary:

Tilmanocept, a new imaging dye made at San Diego Moores Cancer center is shown to have an ability to determine whether a lymph node is cancerous or not. This new imaging dye’s main function is to detect cancerous sentinel lymph nodes inside a surgery room, and how far the cancer has spread throughout the body. In March, it received the US FDA’s approval for usage. Tilmanocept is a major step towards fighting breast cancer. This imaging dye can help doctors identify cancerous lymph nodes and can therefore assist doctors in determining which treatment to provide after surgery.

Article 2:

Results from Merck’s Vorinostat phase 1 trial on lymphoma

Published on February 5, 2013

Patients whose aggressive lymphomas have relapsed or failed to respond to the current front-line chemotherapy regimen now have an effective second line of attack against their disease. Reporting the results of a first-of-its-kind phase 1 clinical trial to test the effectiveness of a new class of drugs to augment standard chemotherapy, a team led by Fred Hutchinson Cancer Research Center scientists found that giving patients high doses of Vorinostat (suberoylanilide hydroxamic acid) in combination with another round of commonly used second-line drugs resulted in a 70 percent response rate, including several patients whose lymphoma cells disappeared entirely.

According to Ajay Gopal, M.D., associate member of the Fred Hutch Clinical Research Division and corresponding author of the paper, published online in the British Journal of Haematology, the study results open the way to potentially solve the dilemma of how to effectively treat patients when modern cancer drugs fail after the first try. And, he said, it sets the stage for using a new class of drugs called histone-deacetylase inhibitors (HDAC), of which Vorinostat is one, to sensitize tumor cells to the cancer-killing effects of chemotherapy.

Patients treated in the trial had several types of lymphoma, however the best responses were seen in those who had Hodgkin and diffuse large B-cell lymphomas, two of the most aggressive types that typically require a stem cell transplant to cure if they are not cured after the first line of treatment. Knocking back the cancer raises the likelihood for a successful transplant.

"The better the response, the better the outcome will be when patients proceed to a stem cell transplant designed to cure them of their disease," said Elizabeth Budde, M.D., Ph.D., a research associate in the Fred Hutch Clinical Research Division and first author of the study.

The researchers noted that while the current front-line chemotherapy drugs are the most effective yet against lymphomas, patients who relapse after receiving them are less likely to achieve long-term, disease-free survival when current second-line or "salvage" therapies are applied. This is because the cancers develop resistance to the drugs or the tumor's biology changes in some way to reduce their effectiveness.

Lymphoma refers to a group of cancers that strike the lymphatic system, which is a key part of the immune system. Lymphomas are broadly classified as either Hodgkin or non-Hodgkin. Some lymphomas are highly curable; others require complex treatment.

Summary:

Lymphoma, a disease that can cause tumors, can be cured, but some patients that have a more malignant type of lymphoma may not be as lucky and may require a stem cell transplant. However, a new type of drug called Vorinostat was introduced to the public by the Fred Hutchinson Cancer Research Center. Around 70% of the patients who had acquired lymphoma and tried out Vorinostat ended up with positive results, and some patients showed no signs of having lymphoma afterwards. This solves the problem for what to do after the first type of treatment is ineffective against the lymphoma. If the response is favourable after Vorinostat, there is a high probability that the outcome of the surgery will also be favourable. Although chemotherapy (the first treatment used when a patient has lymphoma) is still the most useful, some patients may develop the same disease again after being cured.

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