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The Immune System of Human Beings

The Immune System of Human Beings

The immune system is the most intricate systems in the human body. The quest to comprehensively understand its working mechanism is a daunting task. The understanding of the human body immune system is paramount for healthcare practitioners while in practice. In the most universal sense, the immune system stands as the mechanism, which makes it possible for living organisms to distinguish between “non-self” and “self”. Early discoveries of the immune system were fueled, to a great extent, by the goal of preventing diseases from spreading and developing better forms of treatment for a set of illnesses. During the ancient times, microbiology experts purposed to vaccinate people who were healthy against contracting diseases. In fact, the creation of vaccines was informed by the need to combat sicknesses before it was determined that illnesses are caused by microbes-or that immunized cells were capacitated to kill microbes. While the immune system is flexible because it is constantly learning and adapting, it comprises various proteins, cells, and organs; when functioning properly; it is inconspicuous; when it is weak in terms of fighting diseases, a person falls ill; it is activated by a cluster of different elements that are not recognized by the body.

First Line of Defense: Physical Barriers

The first lines of defense in the immune system of human beings include the skin, body hair, eye lashes, tears, mucus, cilia, the stomach, amongst others. All these elements conspire in swift succession to prevent harmful foreign substances or disease-causing microbes from entering the body. Physical barriers assume a critical role in the course of inhibiting microbes from interacting with tissues that are prone to infection. Cell barriers comprise of a collection of cells that are joined together tightly to prohibit foreign particles from passing through to inner tissues. For instance, the endothelial cells that border blood vessels have cell-to-cell junctions that are extremely tight, and which assume the role of preventing microbes from accessing the bloodstream. Cell junctions have cell membrane proteins that tend to connect to the neighboring cells’ complementary proteins or extracellular matrix (Lumen, n.d.). Tissues that are located in the different parts of the body contain different forms of cell junctions that include desmosomes, tight junctions, and gap junctions as demonstrated in the figure below. Foreign microorganisms could strive to chemically break these substances down, using enzymes that lead to structural damage; invariably creating access points for pathogens.

(Source: Lumen, n.d.)

The above figure depicts some forms of cell junctions that characterize the human tissue. Tight junctions tend to hold two cells that are adjacent to each other together, thereby limiting or preventing the process of material exchange through the spaces from taking place. Desmosomes contain intermediate fibers that resemble the functioning of shoelaces, riveting cells together, thereby permitting the passage of small materials through the emanating spaces. Gap junctions feature as channels between cells that make it possible for them to communicate through signals.

Second Line of Defense: The Innate Immune System

The second line of defense largely comprise of a collection of organs, tissues, and cells that work collaboratively to protect the body from pathogens. If the latter manage to defeat the first line of defense, for instance, when a person cuts their skin leading to contraction of an infection, the second line of defense takes center stage. It plays this role in a series of stages that are collectively known as the immune response. The cells that are involved in the immune response process are called white blood cells or leukocytes that are mandated to search for and destroy substances and organisms that cause diseases. There are various forms of leukocytes, including Neutrophils, T helper cells, Cytotoxic T cells, Macrophages, Dendritic cells, B cells, and Suppressor T cells (West-Eberhard, 2019). In adeptly, tissues and organs are generally known as the lymph system that includes an intricate network of vessels, ducts, nodes, and organs. They comprise of immune cells that protect the human body against harmful invaders.


Phagocytosis feature as an important mechanism that detects and eliminates materials that are potentially pathogenic. It is a cellular process responsible for ingesting and getting rid of particles that exceed 0.5 μm in diameter, including foreign substances, apoptotic cells, and microorganisms. There are cells called phagocytes that engulf or ingest particles or cells-they exist in two forms, including being normal body cells, for instance, white blood cells or existing as free organisms that are single-celled, for instance amoeba. Phagocytosis fulfills its mandate using four distinct steps. The first stage is where the plasma membrane ensnares the particles of food. Secondly, the membrane forms a vacuole to prevent the food particle from escaping. In the third phase, the food vacuole is fused with lysosomes; lastly, lysosomes’ enzymes assume the role of digesting the particles of food (Calder, 2020). The kind of particles that are the white blood cells phagocytose include cells of dead tissues, bacteria, some dust particles, protozoa, and pigments, amongst other extremely small foreign particles.

Immunological Surveillance

Immunological surveillance is a monitoring technique or process of the immune system for detecting and destroying cells that have been infected with virus and transformed through neoplastic process. As such, the immune system is obliged with a very distinct surveillance role against potential tumors. In the course of preventing attacks against the immune system, tumor cells tend to develop a series of strategies to escape surveillance. According to Naja and Hamadeh (2020), evidence to support immune surveillance emanated from both clinical observations and animal models. For instance, mice that has many immunodeficiency poses extreme rates of tumor incidences. Thus, they are more susceptible to chemically induced carcinogen or transplanted tumors. Patients who have undergone immunosuppression reflect high rates of tumors. On the contrary, many more patients tend to develop cancerous cells despite having a normally functioning immune system. This is an indication that tumor causing cells have the capacity to evade immune surveillance. Consequently, one of the important roles that the immunological surveillance fulfills include combating tumors in cells.


Interferons include a collection of cytokine mediators that are critically involved in the process of cellular immune system with respect to the host cells’ viral infection. Consequently, they are part and parcel of the human body’s immune response that combats the cancerous cells and germs in the body. Basically, they trigger the immune system’s killer cells in the wake of combating the invaders. The term “interferons” emanated from the word “interfere” in line with their nature of interfering with viruses so as to prevent them from multiplying, thereby increasing in number. The cells that are virus-infected produce interferons (IFNs) that automatically signal other cells contained in the body to resist the growth of viruses. Matuschek (2020) provide that the role of interferons towards inflammation activation and inflammation cannot be dispensed with. Imperatively, inflammation feature as a vital physiological process that sustains survival when a person is infected with a virus by maintaining the homeostasis of tissues. Together with anti- and pro-inflammatory cytokines, interferons assume a critical role when it comes to putting up the most appropriate response to cells that are damaged, pathogens, and irritants in the course of inflammatory response. The inflammation includes a multi-protein model that initiates cytokines pro-inflammatory cleavage.

Cost Influences of Protein Bars


Inflammation is defined as the response of the immune system towards harmful stimuli, for instance, damaged cells, pathogens, irradiation, and toxic compounds. The process takes place through the removal of destructive stimuli and goes ahead to initiate the healing process. Therefore, inflammation is a defense mechanism that assumes center stage to the health of an individual. When the human body detects a foreign substance, it immediately initiates a biological response in the wake of getting rid of the intruder. The attacker could be a pathogen or a foreign substance, such as an irritant, a thorn, and sundry. Pathogens largely comprise of viruses and bacteria, amongst other organisms that cause infections. At times, the body tends to mistakenly perceive normal cells as destructive, thereby triggering a reaction that cause autoimmune diseases, for instance Type 1 Diabetes (Sompayrac, 2019). The medical community are of the opinion that inflammation could contribute to a broad variety of chronic complications or diseases. For instance, the metabolic syndrome that include heart disease, Type 2 Diabetes, and obesity. Individuals suffering from these conditions tend to have greater rates of inflammatory builders in their bodies. Definite symptoms, as well as ways of resolving it are available

The Third Line of Defense, Humoral Immunity

This third line of defense is specialized to provide specific resistance. It banks on antigens that are definite substances that dominate foreign microbes. The majority of antigens are proteins that are designed to serve as stimuli responses in the production of the right immune response. As such, this third line of defense against the invasion of pathogens feature as a flexible immune response of the body, which has two main characteristics. The first one is that it is specific, meaning that it is able to determine distinctions between microorganisms and put up the most appropriate response (Sompayrac, 2019). Secondly, it is flexible in that it is able to produce heightened responses when re-exposed-suggesting that it has a reliable memory,

 Antibody Structure and Classes

Five major classes characterize the divisions of antibodies. They include IgG, IgM, IgD, Iga, and IgE. These classifications are determined by the immune function, as well as consistency in region structure. The variable region is fashionably divided into framework (FR) and hypervariable (HV) regions in the context of heavy and light chains. The sub-topic can also be understood from the context of immunoglobulin structure, which are a cluster of glycoproteins based on structural and chemical differences. The five major classes of antibodies that are aforementioned in the second sentence are also called isotypes. Every immunoglobulin contains a pair of small chains, including light chains and heavy chains.

 The Third Line of Defense, Cell-Mediated Immunity

This third line of defense is specialized to provide a specific kind of resistance. It relies on a series of T-cells that enter the bloodstream after which they are conveyed by circulation once they have finalized their development process. Once they are at the organ called peripheral lymphoid, they leave the blood circulation and migrate using the lymphoid channel (Turgeon, 2020). Once they are back to the bloodstream, they recirculate between the peripheral lymphoid to the point that they meet with a particular antigen. This is a kind of adaptive immune system whereby the T-cell must combine with antigens so that they are induced to be able to differentiate and proliferate into cells that are able to actively participate in the elimination process of an antigen.

Vaccines and Pseudoscience

The article provides very vital information about the correlation between vaccines and autism. Accordingly, past researchers have substantiated the reality that there are some vaccines administered during childhood, which cause autism. According to Destefano (2007), the assertion feature as one of the most controversial issues that has marred the field of vaccines in recent years. Specifically, vaccines, such as thimerosal-containing vaccines (TCVs) and measles-mumps-rubella (MMR) predispose an individual to autism. The article categorically ascertains that coverage is hampered by changes in the criteria used for diagnostics. Another hindrance includes recognition and increased awareness of autism. One possible evidence used to support the thesis statement includes a Montreal-based study that determined that prevalence of birth cohort of pervasive disorders of development, including autism, grew from 1987 to 1998 (Destefano, 2007). Imperatively, during the same period, coverage of MMR vaccination demonstrated an empirical decrease. It means that there are no studies that have determined a definite association between autism and MMR vaccination.



Human being’s immune system’s tend to learn and adopt and makes it objective and effective in dealing with a host of emerging biological invaders. At their weakest point, an individual falls ill since the unrecognized foreign substances have found their way into the body and incapacitated its functioning altogether. The system is rather complex as it comprises of many elements that work together in different capacities to fulfill one and the same purpose. They include First Line of Defense: Physical Barriers, Second Line of Defense: The Innate Immune System, Phagocytosis, Immunological Surveillance, Interferons, and The Third Line of Defense, Cell-Mediated Immunity, amongst others. All of these elements are specialized with a host of different capacities but are conjoined together under the same goal of protecting the body against foreign invaders, such as pathogens.


Abbas, A. K., Lichtman, A. H., & Pillai, S. (2019). Basic immunology e-book: functions and disorders of the immune system. Elsevier Health Sciences.

Calder, P. C. (2020). Nutrition, immunity and COVID-19. BMJ Nutrition, Prevention & Health3(1), 74.

Destefano, F. (2007). Vaccines and Autism: Evidence does not Support a Causal Association. Clin Pharmacol Ther. 82(6): 756-9.

Fischer, J. C., Zänker, K., Van Griensven, M., Schneider, M., Kindgen-Milles, D., Knoefel, W. T., … & Matuschek, C. (2020). The role of passive immunization in the age of SARS-CoV-2: an update. European journal of medical research25, 1-6.

Lumen. (n.d.). Physical Defenses. Retrieved from:

Naja, F., & Hamadeh, R. (2020). Nutrition amid the COVID-19 pandemic: a multi-level framework for action. European journal of clinical nutrition74(8), 1117-1121.

Sompayrac, L. M. (2019). How the immune system works? John Wiley & Sons.

Turgeon, M. L. (2020). Immunology & Serology in Laboratory Medicine-E-Book. Elsevier Health Sciences.

West-Eberhard, M. J. (2019). Nutrition, the visceral immune system, and the evolutionary origins of pathogenic obesity. Proceedings of the National Academy of Sciences116(3), 723-731.

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By Hanna Robinson

Hanna has won numerous writing awards. She specializes in academic writing, copywriting, business plans and resumes. After graduating from the Comosun College's journalism program, she went on to work at community newspapers throughout Atlantic Canada, before embarking on her freelancing journey.

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