THE IMMUNE SYSTEM
The immune system is a host defense system made up of numerous biological processes and structures within an organism that shields it against disease. For the immune system to function accordingly, it must be able to detect a wide variety of agents, referred to as pathogens, ranging from parasitic worms to viruses and differentiate them from the healthy tissue of the organism. In a significant number of species, there are two main subsystems of the immune system; the adaptive immune system and the innate immune system ( Marcus, 2019). These subsystems capitalize on cell-mediated immunity as well as the humoral immunity to undertake their roles. For instance, in humans, the blood-brain barrier, similar fluid–brain barriers, and the blood-cerebrospinal fluid barrier separate the neuroimmune system, which protects the brain from the peripheral immune system ( Jones, 2013). The immune system comprises of three lines of defense facing foreign invaders. The antecedent line of the defense includes the physical and chemical barriers, which are contemplated innate immunity functions. The second line of defense constitutes the nonspecific resistance, which is also contemplated as an intrinsic immunity function. Lastly, the third line of defense represents the specific resistance, which is also considered an acquired immunity function. This paper will elaborate on the functioning of the three lines of defense in the immune system.
Antecedent to triggering of any immune factors, the skin, which is also referred to as the epithelial surface, acts as an impassable, continuous barrier to probably infectious pathogens. As a result, the skin is considered the innate immune system’s first defense (( Jones, 2013). Pathogens are inactivated or killed on the surface through drying out or desiccation as well as by the aid of the skin’s acidity. Besides, the beneficial microorganisms coexisting on the skin compete with assailing pathogens, thereby preventing infection. Peeling skin or desquamation also assists in dislodging organisms that have adhered to the body’s surface awaiting entry. The areas of the body which are not covered by skin such as the mucous membranes and the eyes hold surrogate defense methods. For instance, the eyes have tears and mucous membranes that dispense partial protection despite allowing absorption and secretion. The mucus secretions trap and rinse away pathogens, while cilia located in the nasal passages and respiratory tract push the mucus along the pathogens out of the body. Moreover, tears and mucus secretions constitute microbicidal factors that diverse infections from entering into the human body through these routes.
In case the pathogens succeed in getting through the first line of defense, for instance, through a cut on the human skin, and as a result, infection is enrooted, the body activates the second line of defense. The second line of the defense comprises tissues, organs as well group of cells which work collectively to safeguard the body. For instance, when the body is invaded by pathogens, the neutrophils assemble at the entry site and work towards engulfing and destroying it. When the pathogens succeed in getting past the neutrophils, the macrophages are attracted by neutrophils’ death throes. These cells endeavor to engulf and destroy the invader while at the same time, sending signals to supplementary cells for help. The dendritic cells, which repeatedly patrol around and can communicate with up to two hundred alternative cells at a go, strive to find the pathogen and communicate with T helper cells assembled in the body’s lymph nodes. In case the T helper cells diagnose the pathogen, they are immediately cloned to boost their numbers before finally activating the indispensable immune cells for the attack.
Antecedent to triggering any immune factors, the skin, which is also referred to as the epithelial surface, performs as an impassable barrier to potentially-infectious pathogens (Jones, 2013). The skin is considered the first defense of the innate immune system; it is the first of the nonspecific barrier defenses. Pathogens are killed or inactivated on the skin by the skin drying out and by the skin’s acidity (Marcus, 2019). Also, beneficial microorganisms that coexist on the skin compete with invading pathogens, preventing infection. Desquamation, or peeling skin, also serves to dislodge organisms that have adhered to the body’s surface and are awaiting entry. Regions of the body that are not protected by skin (such as the eyes and mucous membranes ) have alternative defense methods. These include tears in the eyes; mucous membranes that provide partial protection despite having to allow absorption and secretion; mucus secretions that trap and rinse away pathogens; and cilia (singular cilium) the nasal passages and respiratory tract that push the mucus with the pathogens out of the body. Furthermore, tears and mucus secretions contain microbicidal factors that prevent many infections from entering via these routes.
Immune surveillance refers to a theory that states that the immune system of an individual patrol can identify and destroy invading pathogens and host cells, which later become cancerous. Although potential cancer cells frequently develop throughout an individual’s life, the immune system destroys them instantly. Joe (2017) argues that there exists some evidence for this theory. Besides, there exists some evidence that the immune system launches an attack against existing cancers, but it often fails. Anderson (2013) argued that for immune surveillance to work against cancer, cancer cells are required to release antigens that do not exist in healthy cells. Otherwise, an individual’s immune system would view them as “self” and therefore tolerate them. Some examples of tumor antigens include antigens represented by cells infected with oncogenic viruses. For instance, as human papillomaviruses,HPV is a risk factor for cervical cancer KSHV as the virus can cause Kaposi’s sarcoma
Inflammation refers to one of the initial responses of the immune system towards infections. Increased blood flow in the tissue leads to swellings, redness, and pain. If the cells are infected or injured, they release cytokines and eicosanoids. Eicosanoids comprise of prostaglandins that produce fever, dilation of blood vessels, and leukotrienes, which attract the leukocytes or (white blood cells). Usually, cytokines such as chemokines, interleukins, and interferons. These cytokines play essential roles, for instance, supervising the communication between leukocytes, chemotaxis promotion, and anti-viral effects such as collapsing the host’s cell protein synthesis, respectively. Besides, cytotoxic factors and growth factors also control inflammatory response through the immune cell recruitment to the site of infection as well as promoting removal of pathogens and recovery of the damaged tissues.
The third line of defense is involved in case the first and second lines of defense break down (Lucas et al., 2019). This defense incorporates a specific response for every distinct pathogen, leading to adaptive immunity, which is moderated by specialist Lymphocytes, i.e., Cell-mediated immunity, or antibodies, i.e., humoral immunity. Humoral immunity and Cell mediated immunity comprises foreign matter recognition in the body. Body cells are referred to as “self while the foreign cells are referred to as “non-self.” The distinction between self cells and non-self cells is the proteins on the cell membrane ( Jones, 2013). The cell membrane proteins are referred to as MHC class markers. Besides, they are coded for by genes and function as cell antigens. These two MHC marker classes exist in MHC class constituted in all cells, while the MHC class II and red blood cells exist only in T and B cells and a few macrophages. These antigens subsist molecules, often proteins that trigger an individual’s body immune responses, only start in case of detection by B and T cells.
An antibody, also referred to as immunoglobulin, is a protective protein produced by the body’s immune system to respond to the invasion of a foreign substance referred to as an antigen ( Hughes, 2016). Antibodies diagnose and close up the antigens to eliminate them from the body. A vast range of substances is treated as antigens by the body, such as toxic materials and disease-causing organisms. In the incident, an alien element infiltrates into the body; the immune system operates it as foreign. This is because the molecules’ antigen’s surface diverges from the ones that are found in the body. For the invader to be eliminated, the immune system calls on several mechanisms, including antibody production, which is one of the most vital tools in the immune system. Antibodies are made by individual white blood cells named B cells or B lymphocytes ( Lucas et al., 2014). At the moment, an antigen pickles to the B-cell’s surface; it prompts the B cell to break down and mature into a cluster of identical cells referred to as a clone ( Jones, 2019). The mature B cells, also known as plasma cells, conceal a significant volume of antibodies into the bloodstream as well as the lymphatic system.
The highly specialized dendritic cells with the role of ingesting and presenting antigens are the essential antigen-presenting cells in the body (Lucas et al., 2014). Tissue dendritic cells digest antigen at the regions of infection and are stimulated as a component of the innate immune response. As a result, these cells induce their movement to resident lymphoid tissue as well as their maturation into cells, which are highly competent at submitting antigen to retraining T cells. Surface molecules are also referred to as co-stimulatory molecules that synergize with antigen in the activation of naive T cells and are used to distinguish mature dendritic cells. Besides, the phagocytic cells which provide the first line of defense in opposition to infection can also be triggered to indicate the MHC class II and co-stimulatory molecules. This allows them to function as antigen-presenting cells, even though they are less potent in activating naive T cells than dendritic cells. Once a T-cell response is initiated. Besides, the B cells and macrophages which have occupied specific antigen also turn into targets for armed T cells.
The hypothesis implicates that the measles-mumps-rubella (MMR) vaccine, which may lead to autism, was progressed by Wakefield and colleagues. This is indicated in a report that describes twelve patients having regressive developmental disorders and inflammatory bowel conditions, primarily autism. The authors argue that the MMR vaccine may have led to bowel dysfunction that subsequently caused neurodevelopmental disorders.
Autism constitutes a strong genetic component, and associated neurological defects possibly transpire sooner in embryonic development. Thus, in predominant cases, it is inconceivable that a vaccination given after birth might provoke autism. In some instances, a child might seem to be developing typically but then revert and develop autistic behaviors. Theoretically, a plausible link of biology with vaccination can be made in the cases of regression.
The critical evidence of the with vaccination was that for two-thirds of the cases, the pediatrician mentioned that the MMR vaccine could have led to the generation of behavioral problems. Besides, the authors projected that enduring gastrointestinal tract measles virus infection might have led to the pathologic changes that facilitated gastrointestinal absorption of toxic neuropeptides. As a result, this led to damaging the central nervous system as well as neurodevelopmental regression.
Besides, consequent studies by Wakefield and colleagues fail to support their hypothesis. For instance, Wakefield’s group and other researchers published highly definite laboratory assays in patients having inflammatory bowel diseases. In this essay, the authors imply that there exists no link between autism and the vaccination for the measles virus.
Besides, indirect evidence of the absence of a link between autism and the MMR vaccine is evident in recent ecological studies conducted in California and Great Britain. Every study correlated temporal trends in measles vaccination coverage with ensuing patterns in autism popularity, and neither discovered a positive correlation.
In conclusion, the hypothesis that the MMR vaccine might cause the onset of autism or regression has minimal support. The pressure of the presently available epidemiological, among other complementary evidence dispute against an imaginative association. Therefore, the probability of an idiosyncratic reaction in a given susceptible individual cannot be revoked. These events would have to be too uncommon to trigger obvious increased risks on a community level. An analysis committee from the Institute of Medicine came into similar conclusions.
References
Marcus, N. ( 2019, January 13). The Immune System. The Journal of Improved Health and Vaccination. 7(1). 142-159
Hughes, F. ( 2016, May 14). How an Organism Immune System Works. The Journal of Living things. 7(1-4), 102-116
Lucas, A., Jones, B., & Lucia, J. ( 2014, July 13). The Immune System of a Human Being. WNBD. 144-210.
Mohamed, J. (2013, December 16). T Cell-Mediated Immunity. Immunobiology: The Immune System in Health and Disease. (5), 140-156
Jones, B. ( 2013, February 16). Immunology and Inflammation. Bio connects Life Sciences. (4) 96-103