The world is constantly faced with many pathogenic organisms, whether it be a viruses, bacteria or parasites. Some of these microorganisms are non-pathogenic and can help the human’s natural flora, however if they are pathogenic they may be detrimental to one’s health. The body’s natural way to fight off these infectious organisms is through the human immune system. The human immune system has evolved over time and can detect pathogens, assess the infection, determine the needed response and then attack the invader(1). Researchers throughout the last few decades have attempted to eradicate most diseases, find cures to infection and even prevent disease through manipulation of the immune system. Currently the most common way to prevent infection is through the use of a vaccine(2). Vaccines were first developed by researcher Edward Jenner in the 16th Century where he developed a vaccination that prevents individuals from acquiring smallpox virus(3). Researchers have come a long way since then and have developed many different types of vaccinations. This milestone in immunological research catalysed the experimental research of preventative measures against pathogenic organisms and the development of many of the vaccines we use today. Without the common vaccination protocols that society has implemented and advertised worldwide, the infection and disease outbreak for a lot of common pathogens would be a lot higher.
History of Vaccination
In the past, communities have attempted to use herbal remedies and have experimented with natural solutions to prevent and fight infections. In 1796, researcher Edward Jenner began experimenting with Cowpox to try and find a preventative measure for smallpox (3). His vast knowledge in animal biology human bodily functions gave him the knowledge to understand how the immune system worked in relation to invasion. His knowledge led him to run an experiment testing if someone was infected with Cowpox he believed that they may not get infected with smallpox. He tested his theory on an eight-year-old James Phippes who he infected with Cowpox. He did this by using an inoculation of Cowpox infected pus specimen from a Bristol Milkmaid. Jenner then attempted to infect the boy with the Smallpox virus seven weeks later. He observed as the boy remained unaffected by the smallpox sample and his preventative measure theory had been proven as he exposed the boy on multiple occasion and each time he was unaffected (3). This discovery lead to the first Vaccine being produced worldwide and it was only after then that they had the ability to eradicated smallpox (4). Other researchers such as Alexander Glenny who had a broad understanding of the molecular components of immunological invaders began using chemicals to inactivate tetanus toxins (5). He eventually discovered that the chemical formaldehyde could be used to inactive the tetanus toxin. This discovery had prompted many other researchers to use similar methods by inactivating toxins and introducing them to uninfected patients to boost the person’s immunity (5). In 1938, an improved version of his vaccine was created which proved efficient in preventing tetanus during World War 2, particularly in the military base where tetanus infection was common (5). These discoveries are recognised as massive milestones in immunology and have led to the eradication of many infections and diseases such as Smallpox which is claimed to be eradicated by the World Health Organisation(WHO) in 1980(6).
The Human Immune System
The human body has its own natural defence mechanism against foreign invaders which is known as the Human Immune System. The Human Immune System is composed of many different barriers to prevent attack and the most effective and essential is the Lymphatic organs and cells. The system is firstly composed of physical/chemical barriers to prevent invaders which consists on the skin, cilia in entrance tracts, natural flora, mucus and bodily secretions (7). The second and third line of defence consists of the lymphatic organs which allow the circulation of specialised cells that help to identify and attack pathogenic material. The Lymphatic system produces lymphocytes and leukocytes which are white blood cells that can create antibodies against identified pathogens to help attack the invader (8) . It also producers White Blood Cells(WBC) known as neutrophils, Monocytes, Neutrophils, Basophils and Eosinophils. Some of these cells are known as phagocytes which work to identify and engulf foreign material and digest its contents . Natural Killer Cells also work to attack mutated or infected cells of the hosts body(8). Specialised cells known as B-Cells (B Lymphocytes) and T-Cells ( T-Lymphocytes) circulate the blood stream to fight of infection and disease. B cells are produced and mature in the Bone marrow and react directly to pathogens by producing antibodies(8). T cells are produced in the bone marrow and mature in the Thymus. When a pathogen first enters the body, a macrophage will ingest the pathogen which contains an antigen and display the antigen on its cell surface as a Major Histocompatibility Complex (MHC) marker (9). MHC markers and produced in the Rough endoplasmic reticulum of a cell and are encoded by genes in HLA locus Helper T cells will recognise the MHC which is presented on the surface and become active (10). There are MHC 1 markers which are found on all of the body’s nucleated cells and MHC 2 markers which are found on cytotoxic T cells and antigen presenting cells (9). MHC1 cells present antigens to cytotoxic T cells and MHC 2 presents the antigen to helper T cells. In their active state, they active cytotoxic T cells which kill the infected cells which, T memory cells which will remain in the body for a while after infection incase infection is to occur again. The B cells will then proliferate and into B Plasma cells and B memory cells. Plasma B cells produce antibodies that are able to deactivate a pathogen and the memory B cells also circulate the body incase another invasion occurs to allow a faster response to the pathogen as they can immediately recognise the pathogen and initiate the correct immune response (11). At the end of the infection, Suppressor T cells will become active which stop the immune system once all antigens have been destroyed (11).
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