An explanation of the functions of the white blood cells in the defense against pathogens in human immunity
Introduction
You were cutting onions in the kitchen and you accidentally cut your finger, a few weeks later you cannot feel pain or you see the cut anymore. Have you ever wondered how this happens, how your body is able to heal and keep healthy? Well this happens with the help of the immune system and its associated organs and cells. This paper is going to be explaining the functions of white blood cells in the defence against pathogens and infectious diseases in human immunity and how all the organs and cells associated in the immune system work together to keep the body healthy.
Functions of the white blood cells
White blood cells also known as leukocytes were discovered by Andral (1797-1876) and they are responsible for defending the immune system against foreign invaders and pathogens. White blood cells can be thought as an ‘Antivirus’, that detects, identifies, destroys and removes unwanted and harmful invaders from the body. They originate from the bone marrow and circulate in the blood and lymph fluid. They are also able to leave the blood vessels and migrate to body tissue if are needed there. White blood cells are categorized by the apparent presence or absence of granules in their cytoplasm and they are considered to be a granulocyte (granule present) or an agranulocyte (granule absent) (Bailey, 2016).
Granulocytes
There are three types of granulocytes, the neutrophils, eosinophils and basophils. Neutrophils are the most abundant of granulocyte in the blood and they are chemically drawn to bacteria and migrate through tissue to the site of infection. Neutrophils are phagocytic; they engulf the target cell and destroy it. The neutrophil is also destroyed in the process (Coskun, Dizdar, Baspinar & Ortaköylüoğlu, 2016). The second type of granulocyte the eosinophil is often found in the tissues of the stomach and intestines. Eosinophils are phagocytic and they release a toxic substance (antibodies) that destroys the invaders. These white blood cells are most active during parasitic infections and allergic reactions. The least numerous of all white blood cells the basophil, contains substances that inhabits blood clotting and increases permeability of capillaries to increase blood flow. An increase in blood flow aids a faster transportation of the leukocytes to the infected area. Basophils are also responsible for the body’s allergic response.
Agranulocytes There are two types of agranulocytes, the lymphocytes and monocytes. Lymphocytes are the second most important common white blood cells; their function is to distinguish between normal cells and infected cells or invasive pathogens. Each of the three types of lymphocytes, the T cells, B cells and natural killer cells has this ability. The T cells are responsible for responding to stimuli, for destroying virus detected cells, for providing the immune system with "memory" against past infections and for shutting down T cell-mediated immunity toward the end of an immune reaction. B cells are responsible for secreting antibodies and for circulating through the body and initiate a stronger, more rapid antibody response. Natural killer cells provide non-specific immunity and are responsible for providing rapid responses to viral-infected cells. Monocytes, the second type of agranulocytes are the largest of the white blood cells. They migrate from the blood tissues and develop into macrophages and dendritic cells. Macrophages engulf and digest foreign substances by phagocytosis. Dendritic cells are commonly found in tissue located in areas that come in contact with pathogens from the external environment. Their function is to present antigenic information to the lymphocytes in the lymph nodes and lymph organs (Bailey, 2016).
These organs, the lymph organs form a lymphatic system. A vital part of part of the immune system was discovered by Hippocrates (5th century BC) (cited in Michael, 2006) and it is responsible for transporting foreign substances to the lymph organs for disposal. It transports white blood cells to and from the lymph nodes into the bones and the also lymph transports antigen to presenting cells.
How white blood cells defend the body against pathogens
A successful immune response to invaders requires recognition of the invader, activation of the white blood cells, regulation of the immune system and resolution. In order to destroy invaders, the white blood cells must first recognize them. For recognition to take place the B cells produces antibodies I response to the antigen. The antibody then attaches itself to the invader, not to kill it but to tag it so it can be recognized and destroyed by the other white blood cells. After recognition the white blood cells are then activated, the macrophages and the activated T cells releases substances that lure other white blood cells to the trouble spot. After this the helper T-cells produces communication molecules that are sent out as signals that instructs the other cells as they coordinate the attack. This alarms the immune system and enables it to respond.
As soon as the B cells detect the signal, they respond to the call and come to read the antigen from the surface of the macrophages. The B cell is activated and produces millions of antibodies to the specific antigen in order to attack the invader. These antibodies then send a signal to the other white blood cell to engulf and destroy the antibody and whatever it has captured. Once the number of invaders in the body has dropped and the infection has been resolved, the t cells send a signal to the other white blood cells that informs them to inhabit the immune resolution. This is done because a prolonged activation of the immune response can destroy and damage the healthy cells in the body.
Finally, once the invaders are eliminated most white blood cells self-destruct and are ingested in the body. Those that are spared are kept as memory cells. This step is very important because the immune system is able to remember this specific invader and respond more vigorously to it at the next encounter. This way the body is able to obtain acquired natural immunity.
Conclusion
In conclusion, it’s a very amazing phenomenon how our body can heal and keep healthy without acquiring any artificial antibodies. Through the process of immune response and with the help of the different white blood cells our immune system creates a germ fighting army that is well equipped and ready for any battles. As healthy strong soldiers builds a strong and successful army it’s also our duty to help keep our immune system as healthy as possible to ensure a much more efficient and effective immune response. We are to take care of our health as this helps to boost our immune system, by eating healthy, exercising, getting immunized, enough sleep and avoiding the use of alcohol and smoking as this weakens our immune system.
Reference list
Bailey, R. (2016). White Blood Cell. Journal of white blood cells. Retrieved
from http://biology.about.com/od/cellbiology/ss/white-blood-cell.htm
Coskun, B.D.O. , Dizdar, O.S. , Baspinar, O. , Ortaköylüoğlu, A. (2016, July-August). Usefulness of neutrophil. Journal of Usefulness of the Neutrophil-to-lymphocyte Ratio and Platelet Morphologic Parameters in Predicting Hepatic Fibrosis in Chronic Hepatitis C Patients. Retrieved http://www.annclinlabsci.org/content/46/4/380.abstract?sid=ec9ec5ec-ad6d-404a-8eea-4026627409ba
Delves, P.J. (2016). Overview of the Immune System. Journal of biology of the immune system. Retrieved from http://www.merckmanuals.com/home/immune-disorders/biology-of-the-immune-system/overview-of-the-immune-system
Michael, B. (2006). Hippocrates, Internet Encyclopedia of Philosophy. Retrieved from https://en.wikipedia.org/wiki/Hippocrates
Hajdu, S.I. (2003). The Discovery of Blood Cells. Journal white blood cells, (33). Retrieved from http://www.annclinlabsci.org/content/33/2/237.full