Part 1: The Immune System
Physical Barriers, the First Line of Defense
When the body is attacked, physical and chemical barriers serve as the first line of defense (Ward & Vyas, 2020). The skin, tears, mucus, cilia, stomach acid, urine flow, ‘friendly’ bacteria, and neutrophils are among them (Ward & Vyas, 2020). Pathogenic microorganisms must get beyond this first barrier of protection. If this layer of protection is breached, the body’s second line of defense is triggered. The skin is the body’s biggest organ, serving as a barrier between intruders and the rest of the body. The skin creates a mechanical barrier that keeps water out. Microorganisms that reside on the surface of the skin cannot penetrate it unless it is damaged.
Furthermore, viruses can enter the body through the nose, mouth, and eyes. On the other hand, tears, mucus, and saliva contain an enzyme that helps bacteria break down their cell walls. Those that aren’t killed right away become encased in mucus and ingested. The inner lining of the stomach and lungs generates mucus to trap invading bacteria (Ward & Vyas, 2020). Mucus and trapped particles are moved out from the lungs by cilia in the windpipe. Bacteria, dust, and smoke are examples of particles.
Moreover, germs and parasites that have been ingested are killed by stomach acid. In addition, bacteria in the bladder are flushed away by a person’s urine flow. In addition, the body possesses good bacteria that live on the skin, in the bowel, and in various bodily parts, such as the mouth and stomach, which prevent dangerous bacteria from taking control. Finally, neutrophils are white blood cells capable of detecting, killing, and ingesting pathogens attempting to enter the body (Ward & Vyas, 2020).
The second line of defense, the Innate Immune System
The second line of defense is a broad resistance that eliminates intruders without focusing on specific individuals (McComb et al., 2019). All microorganisms that enter human tissues are ingested and destroyed by phagocytic cells. Macrophages, for example, are cells produced from monocytes, a kind of white blood cell. The second line of defense takes over if pathogens get past the first line of defense, such as a cut in the skin, and an infection develops. The immune system fights these infections through a series of actions known as the immunological response.
White blood cells (leukocytes) are the cells that seek and eliminate disease-causing germs or chemicals. Leukocytes are available in a range of sizes and forms. Even though each cell type has a different job, they all work together to keep the body safe. Neutrophils predominantly fight germs, T helper cells provide signals that direct other cells and other kinds of white blood cells, cytotoxic (killing) T cells pierce the pathogen cell’s walls, allowing the contents to seep out, macrophages clean up the debris left by dead cells, dendritic cells detect the presence of an intruder and give evidence of the invader to T cells in lymph nodes, suppressor T cells switch down the immune system to prevent harm to healthy cells, and B cells generate antibodies (McComb et al., 2019).
The lymph nodes and lymph fluid in the lymphatic system are the tissues and organs involved in the immune system. Each of these has a distinct purpose. White blood cells are present in the lymph fluid, which is carried via the lymphatic system. The lymph nodes filter germs and other foreign materials out of the lymph and expose them to B and T cells and macrophages, which can eat them up.
Phagocytosis
Phagocytosis involves a cell engulfing a particle and forms a phagosome as an internal compartment (Rosales & Uribe-Querol, 2017). It’s a procedure in which a cell attaches to the object it wants to eat on the cell surface and pulls it in a while, engulfing it (Rosales & Uribe-Querol, 2017). Phagocytosis is a cell’s attempt to kill anything, such as a virus or an infected cell, and it’s frequently employed by immune system cells. It is divided into four stages: Phagocyte activation; Phagocyte chemotaxis (for wandering macrophages, neutrophils, and eosinophils); Phagocyte attachment to the Microbe or Cell; and Phagocyte ingestion of the Microbe or Cell (Rosales & Uribe-Querol, 2017).
Monocytes and macrophages, granulocytes, and dendritic cells are the three primary types of phagocytes, each with a somewhat different role in the body (Rosales & Uribe-Querol, 2017). Phagocytosis is a primary process utilized by a multicellular organism’s immune system to eliminate infections and cell debris. The phagosome then digests the ingested substance. Objects that can be phagocytized include bacteria, dead tissue cells, and tiny mineral particles (Rosales & Uribe-Querol, 2017).
Immunological Surveillance
This is a mechanism in which the immune system monitors the body for virally infected and neoplastically altered cells to recognize and kill them (Ribatti, 2016). T cells and NK cells are the cells in charge of immunological monitoring. In the fight against tumors, the immune system plays a crucial role. Tumor cells adopt several ways to evade immune monitoring to avoid being attacked by the immune system (Ribatti, 2016). Animal models and clinical findings both show evidence of immune surveillance (Ribatti, 2016). Tumors generate antigens that may elicit an immune response, according to the immune surveillance theory. Tumor-specific antigens (found only on tumor cells) or tumor-associated antigens (present on both tumor and normal cells but overexpressed on tumor cells) can both activate immune responses (Ribatti, 2016).
Interferons
Interferons are a group of critical proteins generated and released by host cells in response to the presence of viruses (Lazear et al., 2019). A virus-infected cell will often produce interferons, causing surrounding cells to boost their antiviral defenses. Interferons are crucial in the fight against infections because they are the initial line of defense. They alert the immune system to the presence of bacteria or cancer cells in the body (Lazear et al., 2019). Furthermore, they activate killer immune cells to combat the invaders. Interferons get their name because they prevent (interfere) viruses from replicating by interfering with them (Lazear et al., 2019).
Inflammation
Inflammation is a defensive reaction involving immune cells, blood vessels, and molecular mediators when bodily tissues are exposed to damaging stimuli such as infections, damaged cells, or irritants (Chen et al., 2017). Redness, heat, swelling (tumor), and pain are the four cardinal symptoms of inflammation (Chen et al., 2017). Redness arises from the dilation of small blood vessels in the damaged area. The immune system’s reaction to damage an illness includes inflammation (Chen et al., 2017). It’s the body’s way of telling the immune system to mend and restore damaged tissue while also defending against external invaders like viruses or bacteria (Chen et al., 2017).
The Third Line of Defense, Humoral Immunity
Antigens, which are particular chemicals present in foreign microorganisms, are used in this technique (Tangye & Ma, 2019). Antigens trigger the immune system to respond. Humoral immunity involves the generation of antibodies and all of the processes that occur as a result of it (Tangye & Ma, 2019). Antibody effector actions include pathogen and toxin neutralization, classical complement activation, and opsonin stimulation of phagocytosis and pathogen elimination. Humoral immunity is a kind of immunity controlled by macromolecules in extracellular fluids such as released antibodies, complement proteins, and some antimicrobial peptides (Tangye & Ma, 2019).
B cells have a role in humoral immunity. The amount of circulating B cells remains constant throughout life. To become activated, B cells require two signals. T cells are essential for maximum antibody production since most antigens are T-dependent. The initial signal from a T-dependent antigen comes from antigen cross-linking BCR, and the second comes from the Th2 cell. Protein is included in T-dependent antigens so that peptides may be displayed on B cell Class II MHC to Th2 cells, which subsequently give co-stimulation to cause B cell proliferation and differentiation into plasma cells (Tangye & Ma, 2019). T-dependent antigens cause isotype flipping to IgG, IgA, IgE, and memory cell formation.
The Third Line of Defense, Cell-mediated Immunity
Cell mediate immunity refers to T-cell activation by a particular antigen (Vaeth et al., 2020). There are millions of distinct T-cells in the body, each capable of responding to one specific antigen. The third line of defense is the specific immune system, which consists of lymphocytes such as B- and T-cells that are primarily triggered by dendritic cells. Immune responses that do not include antibodies are known as cell-mediated immunity (Vaeth et al., 2020). In response to an antigen, cell-mediated immunity involves the activation of phagocytes, antigen-specific cytotoxic T-lymphocytes, and the production of different cytokines. Cell-mediated immunity is dubbed after the T cells’ ability to hook on to the invader’s antigens and start responses that result in the elimination of non-self materials.
Finally, when it comes to the immune system, vaccinations play a role. A vaccination is a chemical that aids in the prevention of specific illnesses. Vaccines include a microorganism that is either dead or weakened. It aids the immune system in recognizing and eliminating the live germ in the event of a subsequent infection.
Part 2: COVID-19
2019 ended with discovering a new virus, subsequently dubbed a novel Coronavirus (World Health Organization, 2021). The first outbreak was discovered in Wuhan, Hubei Province, China (World Health Organization, 2021). Despite China’s efforts to confine the epidemic inside Hubei, the virus spread swiftly throughout the world. This virus poses a public health risk because it spreads from person to person in close quarters. Several individuals have died and continue to test positive and die many months into the epidemic because the world was not equipped to respond quickly enough to a virus of this size.
Within a six-foot radius, the virus spreads and multiplies fast from host to host by moisture droplets in the air exhaled by an infected individual (World Health Organization, 2021). Another way for the virus to spread is through infected surfaces where the air is still breathable. The virus may persist on such surfaces for three to seventy-two hours after being contaminated by an infected human (World Health Organization, 2021). It usually spreads when an infected person coughs, sneezes, or breathes in the surrounding air. Infections begin when dangerous germs enter the body through the nose, mouth, eyes, and ears. Microbes enter the body through open passages such as the nose and mouth, defeating our initial line of defense. Once inside, our immune system goes to work attacking the virus, also referred to as our second line of protection. The virus infects the body if the immune system fails to protect it (World Health Organization, 2021).
Antibiotics cannot be used to treat viruses because viruses have considerably higher antibiotic tolerance (World Health Organization, 2021). Antibiotic resistance in herds is exacerbated by poor cleanliness, overcrowding, and fast movement. Gram-negative bacteria, primarily Enterobacteriaceae, are susceptible to this resistance and can behave as pathogens, causing illnesses. Immunity plays a vital role in combating infection, and it employs a variety of strategies to do so. COVID-19, on the other hand, does not make individuals immune, and there is no antiviral medicine available (World Health Organization, 2021). Immune cells, commonly referred to as white blood cells, protect the body in several ways. Macrophages are white blood cells that consume and digest infections as well as dead or dying cells. Macrophages trigger antibodies to fight harmful antigens. B-lymphocytes generate antibodies that fight the virus when macrophages fail to block the virus from infecting white blood cells. T-lymphocytes assault cells in the body that the infection has already damaged in the third line of defense (World Health Organization, 2021). Vitamins D and C help build up an immune system against this type of virus. Still, the vaccine, which supplies or promotes the formation of antibodies to an organism that the body has not yet encountered, is the most radical protection against COVID-19 (World Health Organization, 2021).
After months of research, testing, and development, Pfizer and Biotech have collaborated to create a vaccine against COVID-19. The BNT162b2 vaccination in a two-shot dose has been authorized and is now accessible (World Health Organization, 2021). This vaccine relies on messenger RNA, a genetic material that our cells read to produce proteins (World Health Organization, 2021). The mRNA is encased in oily bubbles made out of lipid nanoparticles that protect it when administered. This vaccination aids in the development of immunity to the COVID-19 virus (World Health Organization, 2021). The vaccine’s T-lymphocytes and B-lymphocytes combat the virus. This vaccination works in conjunction with the immune system to assist the body in combating viral exposure.
References
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McComb, S., Thiriot, A., Akache, B., Krishnan, L., & Stark, F. (2019). Introduction to the Immune System. Methods In Molecular Biology, 1-24. https://doi.org/10.1007/978-1-4939-9597-4_1
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