The Effects of Immunosenescence

Introduction

The improvement of healthcare services and the adoption of healthy lifestyles have increased the life span of the American people. Medicaid and long term care service insurance, together with a shift in health behaviors such as the decline in alcohol consumption and smoking, have led to a significant population transitioning to old age (Pawelec, 2018). The population of America is projected to increase to 380 million by 2040 up from the current 320 million. Consequently, the population of the elderly is projected to increase to more than 83 million people from 48million over the same time span (Pawelec, 2018). As people advance in age, they become susceptible to various diseases as a result of the deterioration of their immunity. Immunosenescence is a condition undergone by the elderly as a result of immune system age-related alterations. Immunosenescence is a biological issue that affects the immunity of the elderly from the cellular level and has had economic implications on America’s healthcare sector and labor production.

Physiological Effects of Immunosenescence

The gradual reduction in tissue homeostasis and physiological functioning of the body are some of the changes that accompany aging (Giefing-Krol et al. 2015). The age triggered changes lowers both the adaptive and innate immunity of the body rendering it highly vulnerable to diseases that ultimately cause death. The immune system protects the body against pathological attacks from fungi, bacteria, and viruses. Additionally, the system is mandated to remove allergenic or toxic substances and elimination of senescent cells. Immunosenescence compromises these functions of the immune system, thereby exposing the body to attack from various diseases. The body’s physiological functions directly related to the immune system also get compromised (Costantini, D’Angelo & Reale, 2018). These include the production of the immune cells that are used by the body to monitor and mount a defense against an impending pathogenic attack that stall as a result of the alteration of the system. Aging-associated changes, therefore, cause pathophysiological concerns on the immunity of the elderly.

Effects Of Immunosenescence On Body’s Immune Cells

The immune cells mount the first line of protection against the disease-causing pathogens hence hindering their entry and consequent distribution in the body (Giefing-Krol et al. 2015). During acute inflammation or damage of the body tissues, the first line of immune cells that are called to action is the neutrophils. Neutrophils produce antimicrobial peptides, degenerative enzymes, and reactive oxygen species, all of which counter the microbial activities. Aging and hence leads to the production of immature neutrophils and the overproduction of reactive oxygen species (Costantini, D’Angelo, & Reale, 2018). The alteration of the neutrophil functionality leads to a compromised response system to inflammation in tissues and microbial invasion. Monocytes are another group of immune cells that serve as starters of the response to inflammation. The cells differentiate into dendritic cells and macrophages (antigen-presenting cells). Macrophages that mount inflammatory responses depict two phenotypes: M1, the classical phenotype, and M2 phenotype, depending on the prevailing microenvironment (Giefing-Krol et al. 2015). In healthy people, M1 and M2 are at balance but become imbalanced under chronic inflammation. Aging also causes the imbalance of M1 and M2, leading to age-related disease occurrence.

Dendritic cells connect innate and adaptive immunity. The cells comprise of myeloid and plasmacytoid dendritic cells that are antigen-presenting cells which uses pattern recognition receptors to detect pathogens (Fulop et al. 2018). Additionally, dendritic cells also contain TLR, RLRs, and ALRS. The expression of the TLRs in the aged changes at both intracellular and extracellular levels. The general alteration in the expression of the dendritic cell impacts negatively on the immune response on the aged against bacterial and viral invasion. Adaptive immunity comprise B cells and the T cells (Costantini, D’Angelo, & Reale, 2018). Immunosenescence causes changes starting from the hematopoietic generation, which results in lowered antibody specificity and reduction in cell diversity. Aging alters the affinity, antibody specificity, and isotype, a phenomenon that explains the heightened vulnerability of the elderly to infections. Another type of regulatory cell of the adaptive immunity apart from the B cells is the T cells. Its subsets are CD4+, CD8+, and natural killer cells. All these T cells are produced in the thymus gland, whose integrity reduces with the advancement in the age of an individual. As a result, the expression of CD28, CD27, CD40L (co-stimulatory molecules) is diminished (Fulop et al. 2018). These molecules are responsible for the stimulation of the proliferation of naïve T lymphocytes to activity during the pathogenic attack, and the loss of their expression, therefore, is detrimental to the immune system’s response towards the pathogen. The loss of their expression is often followed by a lowered immunity to vaccination in the elderly as a result of alterations in the second messenger signal pathways.

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Immunological Concern Of Immunosenescence

Immunosenescence compromises the immune system of the elderly by reducing the ability of their bodies to mount an effective defense against pathogenic invasion (Fulop et al. 2018). Following this reduction in the immune system’s effectiveness, the elderly get exposed to attack from various disease-causing pathogens such as bacteria, viruses, and fungi. Besides, Immunosenescence has also been shown to interfere with the body’s response to vaccination as a result of alteration in the signalling pathways, a phenomenon that occurs following changes in the secretion of the second messenger molecules that mediate cellular interaction with the vaccines (Pawelec, 2018). Despite the changed health practices and the improved healthcare services that have served to lengthen the life span of the Americans, Immunosenescence threatens to thwart all the efforts put in place to ensure old lives the longest life possible.

Economic Concerns And Data

Aging and Immunosenescence have negatively impacted the economy of the United States of America’s economy. The most productive population of America is the elderly comprising of those having 65 years and above. Immunosenescence reduces the effectiveness of the immune system of individuals found within this age bracket due to lowered immunity (Lee, Ercius & Smith, 2009). As a result, they get exposed to opportunistic diseases such as influenza and pneumonia. This has cost the American economy over $ 40 billion through healthcare expenditures and productivity losses. There have been heightened social and economic infection costs that have encompassed the treatment of acute infections and long-term health maintenance costs (Aiello & Dowd, 2013). Attack by pneumonia in midlife, for instance, have consequential long-term development of cardiac, dementia, and respiratory conditions that require hospitalization bloating the treatment and care costs.

As a result of aging, hospitalization from infectious diseases in the elderly accounts for 20% compared to other causes of hospitalization of people from the same age group (Aiello & Dowd, 2013). Several vaccines have been developed to boost immunity against infectious diseases among the elderly, which include pneumococcal vaccine, influenza vaccine, and the tetanus vaccine. However, due to Immunosenescence, their protection against infectious diseases is still suboptimal (Lee, Ercius & Smith, 2009). Influenza and pneumonia prevalence rates remain high despite the high vaccination rates put forward against them (59.9% pneumococcal vaccination, 61.3% influenza). They are still the leading cause of hospitalization and subsequent deaths in the elderly (Aiello & Dowd, 2013). Given that the elderly constitute America’s most productive age group, the weakening of their immune system and subsequent hospitalization due to invasion by the opportunistic infections (influenza and pneumonia) have robbed America’s economy of experienced laborers. A situation that has negatively impacted on the productivity of its various economic sectors (Fulop et al. 2018). Times economic writer Edwardo once cried, “The aging of the American population is carving an unexpectedly broad path of destruction across the economy… Many of our most intractable economic ills can be traced to some degree to this ineluctable fact: American elderly economic power is sickling.”

Economic Model Explanation.

The circular flow diagram is the best economic model that captures the effect of Immunosenescence on America’s economy (Fulop et al. 2018). The model defines the relationship between the firm and the households in the labour market wherein the households sell labour to the firms and get paid incomes in exchange for their labour. The firms heavily relies on the labour from the households for its production purposes that without it, its production activities stall and consequently the economy is affected as the flow of money will also have been hindered (Lee, Ercius & Smith, 2009). America’s economy is dependent on the elderly for labor given their vast experience, and when aging and Immunosenescence affect their active productivity, the whole country’s economy is somehow affected.

Conclusion.

Immunosenescence lowers the immune system of the elderly by altering the integrity of the immune cells and their production glands as a result of aging. This phenomenon has compromised the elderly’s response to vaccination despite the intensified campaigns by the healthcare sector and the massive financial allocation towards the same. The resultant deaths robe the economy of productive laborers aged 65-69 years that the country heavily relies on for the production of goods and services for its population. The health sector should, therefore, come up with potent ways of curing Immunosenescence such as more effective vaccines to boost the immunity of the elderly who suffer from Immunosenescence.

Referenc

Aiello, A. E., & Dowd, J. B. (2013). Socio-economic status and Immunosenescence. In Immunosenescence (pp. 145-157). Springer, New York, NY.

Costantini, E., D’Angelo, C., & Reale, M. (2018). The role of Immunosenescence in neurodegenerative diseases. Mediators of inflammation, 2018.

Fulop, T., Larbi, A., Dupuis, G., Le Page, A., Frost, E. H., Cohen, A. A., … & Franceschi, C. (2018). Immunosenescence and inflamm-aging as two sides of the same coin: friends or foes?. Frontiers in immunology, 8, 1960.

Giefing‐Kröll, C., Berger, P., Lepperdinger, G., & Grubeck‐Loebenstein, B. (2015). How sex and age affect immune responses, susceptibility to infections, and response to vaccination. Aging cell, 14(3), 309-321.

Lee, B. Y., Ercius, A. K., & Smith, K. J. (2009). A predictive model of the economic effects of an influenza vaccine adjuvant for the older adult (age 65 and over) population. Vaccine, 27(16), 2251-2257.

Pawelec, G. (2018). Age and immunity: what is “immunosenescence”?. Experimental gerontology, 105, 4-9.