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The Evolution of Immunity and Immune Systems


Background Information

Immunity is the biological state where an individual has adequate defenses against diseases, infections, and other invasions. At the same time, the individual acquires the ability to tolerate autoimmune diseases and avoid allergies (Nunn and Altizer 36). An immune system, on its part, is composed of numerous biological processes and structures within an individual. It protects the organism against infections (Susser and Stein 23). For the immune system to achieve this objective, it must have the capability to detect a wide range of disease causing organisms, which are often referred to as pathogens. They include viruses, bacteria, and parasitic worms. To maintain good health, the immune system should be able to distinguish such invaders from normal body tissues. A well performing immune system helps an individual to develop immunity.

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Pathogens evolve rapidly to avoid detection by the immune systems. To enhance their efficiency in detecting and combating pathogens, immunity and immune systems need to evolve as well (Shabalina and Koonin 578). It occurs as a result of the evolution of entire systems, variants of pathogens, and individuals over a lifetime. It is also brought about by the frequency of lymphocyte clones within the body of an individual during sickness or infections. It mainly occurs in multi-cellular organisms, such as plants and animals. However, studies have revealed that even simple unicellular organisms like bacteria have immunity and immune systems. Such individuals evolve constantly to deal with emerging threats to their existence (Seifert 67).

There are two major types of immune systems. They include the adaptive and the innate sub-systems. The former offers specific protection to an individual through the use of cells and processes that are highly specialized (Shabalina and Koonin 578). It enables the defense mechanisms within the body to remember a particular pathogen that it has encountered in the past (Liu 8). The presence of the antigens of any foreign molecules within the system triggers an immune response (Machi and McEvoy 23). The body develops antibodies to defend itself from the invaders. Consequently, future infections from the pathogen will be detected and dealt with immediately. The innate sub-system, on the other hand, is non-specific. It involves the use of specialized cells and mechanisms to provide immediate response to invasion from pathogens. In most cases, it is observed in primitive organisms, such as insects, fungi, and plants.

The evolution of immunity and immune systems may occur as a result of changes in the incidence of lymphocyte replicas. Such replications are brought about by infections. T-cells are the lymphocytes that confer cell-mediated immunity to individuals. In the recent past, these cells have exhibited the capability to help an organism combat a wide variety of pathogens (Zhou and Rana 98). They achieve this due to the presence of numerous T-cell receptors (TCR). During their lifetime, one is bound to experience numerous infections (Rothenberg and Davidson 68). As usual, the T-cells develop receptors on their surface to deal with new pathogens invading the body. As a result of the numerous changes occurring on these cells, they are often referred to as lymphocyte clones.

Theoretical Framework

A number of theories have been developed in relation to the evolution of immunity and immune systems. One of them is the Clonal Selection Theory (Rothenberg and Davidson 68). It attempts to explain the functions of lymphocytes in defending an individual against foreign antigens. It mainly focuses on B-cells. The structures play a major role in conferring humoral immunity. They achieve this through the secretion of antibodies. There are different kinds of B-cells. According to the theory, antigens are specific in nature. As such, they activate only a particular type of B-cells. The activation occurs through the process of selection. The B-cell selected is prompted to multiply, leading to the production of multiple clones. The new clones help in antibody production (Lazzaro and Clark 205). Future invasion by the same antigen will be immediately resisted. The reason is that the individual has enough antibodies already in existence.

The Darwinian Theory is also used to understand the evolution of immunity and immune systems. According to this framework, immunity develops to ensure the continued existence of an individual (Zhou and Rana 99). The theory is based on the presupposition that only the fit survives in nature. In this case, the ability to defend one-self against infectious agents brings about endurance. As pathogens evolve, immunity and immune systems of individuals have to undergo transformation as well (Zhou and Rana 100).

According to Feschotte and Gilbert, the immunity and the immune system evolve to deal with emerging pathogens (287). In spite of this transformation, individuals continue to succumb to illnesses and infections. The immune systems, both innate and adaptive, are capable of detecting some of these invaders. However, they may lack the capability to fight them (Feschotte and Gilbert 287). One such pathogen that the human body has been unable to fight independently is the HIV virus. Researchers have attributed this to the fact that the virus is constantly evolving at a rate higher than that of the immunity and immune systems (Koonin and Wolf 6). It is still unknown whether or not the immunity and immune systems of an individual can combat all foreign agents invading the body (Bellouquid and Delitala 12). As a result, many scientists are working on ways through which better defense mechanisms can be achieved.

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  • Ha: There is a close relationship between the evolution of immunity and immune systems, whole systems, variants of pathogens and individuals over a lifetime, and frequency of lymphocyte clones within an organism during an infection.
  • Ho: There is no relationship between the evolution of immunity and immune systems, whole systems, variants of pathogens and individuals over a lifetime, and frequency of lymphocyte clones within an organism during an infection.

Scientific Approach

Literature Review

The research will use a literature review study design to test the hypotheses. The approach involves the use of secondary research material to gather information on an issue under investigation. The use of the research design has a number of pros and cons. One of the benefits relating to the approach is that it will help the researcher to adopt a wide perspective on the issue of evolution of immunity and immune systems. The reason for this is that there is a wide range of literature touching on the topic (Machi and McEvoy 12). Literature review studies are also less complex compared to other designs, such as experiments. They are also less costly, yet equally effective. In addition, they take a relatively short duration of time to complete. By using the existing literature, the researcher will also keep up with new developments on the issue of evolution of immunity and immune systems. The reason for this is that the research design helps one to gain access to data from recently concluded studies. In this case, the research design will be of benefit to the researcher with regards to the testing of the hypotheses. The findings generated will be based on up-to-date information. However, the use of existing literature is limiting given that the study can only generate information on what is already known.

Only scholarly articles will be used for the research. In this case, the study will rely solely on books and journal articles. The reason behind this is to enhance the credibility of the findings. In most cases, these scholarly materials are peer reviewed. They are also published in renowned journals. Books are also mainly written by professionals in a particular field, which makes them credible (Machi and McEvoy 16).

Data Bases to be Used

A total of 18 resources will be used in the study. They will be obtained from a variety of online databases, such as PubMed, Google Scholar, Imm Tree, and Genbank.

Search Terms

To access the appropriate resources, a number of search terms will be used. They include:

  1. Evolution of immunity.
  2. Evolution of immune systems.
  3. Evolution of pathogens.
  4. Evolution of lymphocyte clones.
  5. Frequency of lymphocyte clones.

The search terms above will also be used in various combinations.

Inclusion and Exclusion Criteria

An inclusion and exclusion criterion will be used to determine the resources that are relevant to the research. The inclusion criteria will require the title of all books and journal articles to be used in the study to correspond to the topic of evolution of immunity and immune systems. In addition, the resources should be up-to-date. The reason behind this is to provide information that is in line with prevailing trends. The inclusion criteria will also require the sources to be written by scholars and professionals in the field of evolution (Machi and McEvoy 22).

The exclusion criteria, on the other hand, will require the researcher to avoid using resources with titles that do not correspond to the topic (Machi and McEvoy 23). The aim is to ensure that the information gathered is relevant to the study. Books and journal articles published before 2000 will also be avoided.

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The18 resources will provide the information needed to test the hypotheses. The researcher will critically evaluate the literature to deduce information useful to the study. The data collected will be qualitative in nature. It will also be highly segmented. As such, the researcher will ensure that the views of the authors of the resources used are somehow related (Machi and McEvoy 43). Conclusions will be drawn based on the information gathered from the books and journals.


The study will use a wide range of sources of information. As such, it is likely that the authors of some of the books and the journal articles will hold different opinions towards the hypotheses being tested. For example, some of the resources will agree with the null hypothesis. As such, they will be required to effectively prove the close link between the variables. The researcher will use the information to show that all the processes indicated in the hypothesis occur concurrently. Such resources will be used to demonstrate how the processes are linked to one another. To support the claims made, the books and journals will need to have real life examples. The use of examples in scientific papers helps the reader to understand the concept being put across. It becomes easy for them to draw conclusions from the literature provided. Support of the null hypothesis will mean that the evolution of immunity and immune systems will be considered to be a result of three distinct but closely related processes (Duggal and Emerman 689). They include the progression of whole systems, variants of pathogens, and individuals over a lifetime. The other process is the change in the occurrence of lymphocyte clones during an infection.

Some of the books and journals used may reject the null hypothesis. The information in such resources will show that there is no link between the variables (Domingo 31). However, the authors of some of these sources may acknowledge that a form of relationship exists. For example, a particular book or journal article may be used to argue that a relationship does exist between the evolution of immunity, immune systems, and variants of pathogens and individuals over a lifetime (Cortez, Forterre and Gribaldo 65). The same author may fail to recognize that the change in the frequency of lymphocyte clones has an effect on the development of immunity and immune systems. To support their claims, such scholars will use examples. If the null hypothesis is rejected, this will mean that the evolution of immunity and immune systems should be studied as an independent topic.


The findings of the proposed research will have an impact on a number of fields. For example, it is likely to inform policies in the healthcare sector. The results can be used to change the manner in which guidelines are formulated and implemented by the government and other stakeholders in the sector. Information on the evolution of immunity and immune systems would provide health practitioners with a better understanding of the body’s defense mechanism. As a result, interventions to enhance an individual’s ability to combat diseases and infections will be developed. For example, data on frequencies of lymphocyte clones within an organism during an infection will give health researchers valuable insight into the changes associated with the mechanisms employed by an organism to fight invading antigens (Makarova, Wolf and Koonin 4370).

The findings of the study will also have an impact on biotechnologists (Zhou and Rana 97). Using the information provided, they will be able to establish the relationship existing between the evolution of immunity, immune systems, and the other variables identified in the study. Such data can be used to improve interventions in the healthcare sector (Boehm 728). For example, information on the evolution of variants of pathogens and individuals can help practitioners to develop highly effective drugs. At the same time, better preventative measures, such as vaccines, can be developed to help the population fight illnesses and infections (Koonin and Wolf 32).

In addition to the study of the evolution of immunity and immune systems, it will also be important to look into the issue of immuno-deficiency. As such, information on the factors that lead to decreased immunity and poor performance of immune systems will be acquired from the research. It will also be important to study how human interventions can hasten the evolution of immunity and immune systems (Makarova, Wolf and Koonin 4361). As a result, health practitioners can come up with mechanisms to help the body fight pathogens that evolve rapidly. Such pathogens overwhelm the body’s defense systems (Aswad and Katzourakis 631). Through such studies, it would be possible to deal with such health conditions as HIV & AIDS. The infectious diseases continue to kill thousands of people annually across the globe.


Aswad, Amr, and Aris Katzourakis. “Paleovirology and Virally Derived Immunity.” Trends in Ecology Evolution 27.11 (2012): 627-636. Print.

Bellouquid, Abdelghani, and Marcello Delitala. Mathematical Modeling of Complex Biological Systems a Kinetic Theory Approach, Boston: Birkhaeuser, 2006. Print.

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Boehm, Thomas. “Evolution of Vertebrate Immunity.” Current Biology 22.17 (2012): 722-732. Print.

Cortez, Diego, Patrick Forterre, and Simonetta Gribaldo. “A Hidden Reservoir of Integrative Elements is the Major Source of Recently Acquired Foreign Genes and ORFans in Archaeal and Bacterial Genomes.” Genome Biology 10.1 (2009): 65. Print.

Domingo, Esteban. Origin and Evolution of Viruses. 2nd ed. 2007, Amsterdam: Elsevier Academic. Print.

Duggal, Nisha, and Michael Emerman. “Evolutionary Conflicts between Viruses and Restriction Factors Shape Immunity.” Nature Reviews Immunology 12.1 (2012): 687-695. Print.

Feschotte, Cedric, and Clement Gilbert. “Endogenous Viruses: Insights into Viral Evolution and Impact on Host Biology.” Nature Review Genetics 13.1 (2012): 283-296. Print.

Koonin, Eugene, and Yuli Wolf. “Is Evolution Darwinian or/and Lamarckian?” Biology Direct 4.42 (2009): 4-42. Print.

Lazzaro, Brian, and Andrew Clark. “Rapid Evolution of Innate Immune Response Genes.” Rapidly Evolving Genes and Genetic Systems 6.28 (2012): 203-210. Print.

Liu, Ying. Advances of Computational Intelligence in Industrial Systems, Berlin: Springer-Verlag, 2008. Print.

Machi, Lawrence, and Brenda McEvoy. The Literature Review: Six Steps to Success, Thousand Oaks, California: Corwin, 2009. Print.

Makarova, Kira, Yuri Wolf, and Eugene Koonin. “Comparative Genomics of Defense Systems in Archaea and Bacteria.” Nucleic Acids Research 41.8 (2013): 4360-4377. Print.

Nunn, Charles, and Sonia Altizer. Infectious Diseases in Primates: Behavior, Ecology and Evolution, Oxford: Oxford UP, 2006. Print.

Rothenberg, Ellen, and Eric Davidson. “Regulatory Co-Options in the Evolution of Deuterostome Immune Systems.” Innate Immunity 12.6 (2002): 61-88. Print.

Seifert, Steven. Evolution of Microbial Pathogens, Washington, D.C.: ASM, 2006. Print.

Shabalina, Svetlana, and Eugene Koonin. “Origins and Evolution of Eukaryotic RNA Interference.” Trends in Ecology Evolution 23.10 (2008): 578-587. Print.

Susser, Mervyn, and Zena Stein. Eras in Epidemiology: The Evolution of Ideas, Oxford: Oxford UP, 2009. Print.

Zhou, Rui, and Tariq Rana. “RNA-Based Mechanisms Regulating Host–Virus Interactions.” Immunological Reviews 253.1 (2013): 97-111.

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