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Adaptive Immunity sub-divides into B cells and T cells 

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Adaptive Immunity sub-divides into B cells and T cells 

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These cells are also known as lymphocytes, which attack organisms that slip through the first line of defence (innate immunity) and are much longer lived than their related innate cells. Both T-cells and B-cells have a long duration of formation due to their ability of developing behaviours from learned experiences. These cells remember. Meaning, these cells are able to remember foreign invaders following an initial encounter and adapt to melee the intruders the next time they enter the body.

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Article References:

1. Buchmann, K. (2014). Evolution of Innate Immunity: Clues from Invertebrates via Fish to Mammals. Frontiers. https://www.frontiersin.org/articles/10.3389/fimmu.2014.00459/full

2. Flajnik, M. F., & Kasahara, M. (2010). Origin and evolution of the adaptive immune system: genetic events and selective pressures. Nature reviews. Genetics, 11(1), 47–59. https://doi.org/10.1038/nrg2703

3. Hirano, M. (2011). The evolution of adaptive immunity in vertebrates. PubMed. https://pubmed.ncbi.nlm.nih.gov/21569914/

4. Nicholson L. B. (2016). The immune system. Essays in biochemistry, 60(3), 275–301. https://doi.org/10.1042/EBC20160017

5. Tupin, E. (2007, May 8). The unique role of natural killer T cells in the response to microorganisms. Nature Reviews Microbiology. https://www.nature.com/articles/nrmicro1657?error=cookies_not_supported&code=236f7863-0610-4c75-b451-805b93ea7ed9#:%7E:text=Natural%20killer%20T%20(NKT)%20cells,of%20the%20innate%20immune%20response.

Image References:

1. https://www.google.com/search?q=adaptive+immune+system&sxsrf=ALeKk020awp0eKHhHlKzHQjDYyz8Yxwkig:1618263834754&source=lnms&tbm=isch&sa=X&ved=2ahUKEwjisJfI1vnvAhVIqZ4KHSNDBUwQ_AUoAXoECAEQAw&biw=1381&bih=734#imgrc=tois3QmeZkd0jM

2. https://www.google.com/search?q=immune+system&tbm=isch&ved=2ahUKEwjp7d725vnvAhUSlJ4KHQQEAJ4Q2-cCegQIABAA&oq=immune+system&gs_lcp=CgNpbWcQAzIHCAAQsQMQQzIECAAQQzIECAAQQzIECAAQQzIECAAQQzIECAAQQzIECAAQQzIECAAQQzIECAAQQzIECAAQQ1CGnwlYhp8JYOaiCWgAcAB4AIABqQGIAakBkgEDMC4xmAEAoAEBqgELZ3dzLXdpei1pbWfAAQE&sclient=img&ei=Q9B0YKnAFZKo-gSEiIDwCQ&bih=734&biw=1331#imgrc=u1HovOiUVQbvfM

3. https://www.google.com/search?q=natural+killer+t+cells&tbm=isch&sxsrf=ALeKk03bh6iiB4a01KB0JKz9I1Na4Ipq_w:1618268775378&source=lnms&sa=X&ved=0ahUKEwjkoYf86PnvAhWEt54KHfqgA4UQ_AUIECgC&biw=1331&bih=734&dpr=2#imgrc=Mdfm-OGm5W7S5M

4. https://www.google.com/search?q=t+cell+and+b+cells+in+immune+system&sxsrf=ALeKk00QGmA0uEYaPrc_OLK3xT9Bhv74cA:1618268865813&source=lnms&tbm=isch&sa=X&ved=2ahUKEwjv3Jan6fnvAhXM-J4KHVFfC7QQ_AUoAXoECAEQAw&biw=1331&bih=734#imgrc=dY5ttnmlGkZ62M

5. https://www.google.com/search?q=adaptive+immune+system&tbm=isch&ved=2ahUKEwj2jq_g6fnvAhWVqp4KHQjkCDMQ2-cCegQIABAA&oq=adaptive+immune+system&gs_lcp=CgNpbWcQAzIECCMQJzICCAAyAggAMgIIADICCAAyAggAMgIIADICCAAyAggAMgIIADoECAAQQzoGCAAQBxAeUJTBAVjx2AFg6doBaABwAHgAgAGtAogBxQ6SAQcwLjguMS4xmAEAoAEBqgELZ3dzLXdpei1pbWfAAQE&sclient=img&ei=OdN0YLaOLZXV-gSIyKOYAw&bih=734&biw=1331#imgrc=H8IOqWC-XYQtUM

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7. https://www.google.com/search?q=innate+immune+system&sxsrf=ALeKk02VWkOvbfA_gjn-dMDVbzFRgD2lDw:1618285959045&source=lnms&tbm=isch&sa=X&ved=2ahUKEwj_j-_9qPrvAhWTrZ4KHV2QAxYQ_AUoAXoECAEQAw&biw=1331&bih=734#imgrc=dOfTQuFseqw9ZM

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The B cells are known as the center of the adaptive humoral immune system and are thus generally responsible for mediating the production of antigen-specific immunoglobulin which are used to protect against invasive pathogens. These cells function in fighting viruses and bacteria by creating Y-shaped proteins known as antibodies, that attach onto the invading cells and label them for destruction by other immune cells. Interestingly, B-cells at times inhibits the development of tumors by producing antibodies that attack oncogenic viruses and or cancer cells. Furthermore, B-cells are also able to release immune-suppressive cytokines that stifle an anti-tumor response. However, on the downside, these cells when compared to T-cells are far more likely to mutate into liquid cancers such as B-cell lymphoma which has a 5-year relative survival rate. Yikes!

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The T cells are responsible for recognizing and killing infected cells. However, it’s important to note that T-cells divide into two main types, one being the Helper T-cells and the other being the Killer T-cells. The first type of T-cells known as the Helper T-cells work by stimulating B-cells to produce antibodies that in the development of the second type of T-cells the Killer T-cells. With the development of the Killer T-cells, the ability for killing cells that have been infected/ invaded by foreign intruders. It’s important to note that these cells also have the ability to use cytokines (signaling molecules that mediate and regulate immunity, inflammation, and hematopoiesis), as messenger molecules to deliver chemical instructions to the rest of the immune system to enable an increase in responses.

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An example of adaptive immunity includes vaccines. Vaccines work in different ways to provide protection to our immune system. However, The result of vaccines remains the same, with a supply of t-lymphocytes and b-lymphocytes that recognize and combat the invading viruses in the future. In order for this process to occur, certain molecules from the pathogen (known as antigens) must be introduced to the body resulting in the triggering of an immune response.

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Adaptive Immunity & Covid 19

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There are currently three main types of covid-19 vaccines that have been authorized and recommended for use. The first vaccine is the mRNA vaccine

which contains materials from the covid virus. This vaccine works by introducing the virus material that instructs our cells on how to create harmless proteins that are unique to the virus. After the copies of the proteins are made they begin to destroy the genetic material from the vaccine. The second type is the protein subunit vaccines. This type of vaccine contains a small piece of the proteins present in the virus. Once vaccinated with the protein subunit, our bodies recognize the protein as an invader and begin to build T-lymphocytes and antibodies that will remember how to fight the covid 19 viruses in the future. Lastly, we have the vector vaccines. These vaccines use a modified version of a different virus (the vector) to deliver important instructions to our cells. Using these instructions, our cells make copies of the protein. This in turn prompts our bodies to build T-lymphocytes and B-lymphocytes that will recognize and fight the virus if we are infected in the future.

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The mammalian immune system is arguably the most important defense mechanism within higher animals and is all that stands between the pressures of natural selection and the extinction of mammals. Today materializing infection diseases and past pandemics highlights the scope under which our immune system operates, and our understanding now more than ever is crucial in maximizing the potential of the mammalian immune system in order for a favourable outcome. When mentioning mammalian anatomy, the immune system often seems less substantial than organs such as the heart or kidney(s), however the immune system is immense in its active function within the mammalian body, consuming enormous resources in order to produce the sheer number of cells required to function adequately. In the event of pathogen invasion, immune cell(s) respond according to a programme, working swiftly and efficiently in order to eliminate harmful pathogens.

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What is the innate immune system?

The innate immune system is one of two immune responses which act as the first line of defense against harmful pathogens in mammals. The innate immune system also plays a critical role in the activation of certain adaptive immune responses, guiding the directional into a certain effector type. The way innate immune responses work is through the body’s ability to discern features of pathogens that are not found in uninfected hosts. Innate immune responses are effective first responders as they are able to recognize many types of molecules found on microbial surfaces, as well as the double-stranded RNA that comprise certain viruses. Toll-like receptor proteins of innate immune responses work efficiently to recognize pathogen-specific molecules. Amongst the innate immune systems arsenal of pathogen fighting cells are the following and their functions:
basophils: work via fighting parasitic infections, regulating blood (prevent clots), and mediate allergens.

Dendritic cells: work as mediators between innate and adaptive immune system responses. Also responsible for antigen capture, and processing to adaptive immune cells, and their mediation to effector cells.

Eosinophils: responsible for fighting parasitic infections and inflammation, as well as eliminating no-longer-needed cells and regulating bacterial activity.

Langerhans cells: fight against invading microbes in the skin, also aid in recognition of antigens.

Mass cells: are located in the skin and are the first line of defense against pathogens, are primarily known for their role in the homeostasis of the immune system.

Monocytes: specialized white blood cells that work via fighting infections, regulating immunity against harmful pathogens,  and aiding other white blood cells in excreting damaged/dead tissue.

Macrophages: specialized cells which function via phagocytosis of a pathogen (phagocytosis is the process of engulfing of large particles by phagocytic cells). They also responsible for antigen presentation (T cells), and initiate the inflammatory processes of the body via cytokines to activate other cells.

Neutrophils: crucial effector cells that guard against microbial infections and dispose of invading pathogens.

Natural Killer cells: Are activated as a result of macrophage cytokines, work by containing viral infections in preparation for adaptive immune response.

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The adaptive immune system in mammals is centered on lymphocytes bearing antigen receptors which are the result of somatic recombination. The adaptive immune system which came to fruition ~500 million years ago via jawed fish is a complex defense system which is comprised of numerous molecules, tissue and mechanism that all work together to maintain homeostasis within the body. Adaptive immune response is believed to be the result of two macroevolutionary events: recombination activated gene transposon (RAG), and whole-genome duplication (x2 rounds). The two aforementioned features have historically been found in all jawed vertebrates. However, with that being said, jawless fish have been discovered to display an adaptive immune system that is based on a completely set of antigen receptors. With that being said, today the adaptive immune system is thought to have evolved in vertebrates, such that lymphocytes have unique antigen receptors which are the central feature of the AIS. The addition of the AIS to the innate immune system allows for lymphocytes to diversify in their ability to generate antigen receptors in order to recognize and repel harmful pathogens. As a result, all jawed vertebrates assemble their antigen receptor genes via recombination of varying T cell receptor gene segments.

Why do invertebrates not have an adaptive immune system?

Although all multicellular organisms have a form of pathogen defense systems in place, only vertebrates have the addition of the adaptive immune system in place. The reason for this is because invertebrates have adequate immunity to harmful pathogens as a result of existing pathogen detection systems in place (ex: innate immune systems); which leads us to the conclusion that the development of the AIS was not the result of mutational variability of microorganisms.

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The Natural Killer T-cells are also known as lymphocytes that are able to express both T-cell receptors and well as surface receptors for natural killer cells. This in turn enables these cells to be categorized in both innate immunity as well as adaptive immunity. These Natural Killer T-cells further differentiate by how they respond in both systems, of innate and adaptive immunity. For the first, the cells of the innate immune system interact with the infiltrating pathogens by conserved pattern-recognition receptors. While the cells of adaptive immune systems recognize infiltrating pathogens through diverse, antigen-specific receptors.