2021 자율동아리 과학영자신문반 (1) _ The Immune System

(2021 1st semester)

Smallpox is the first and one of the two infectious diseases ever eradicated by mankind. Smallpox brings severe skin eruption and dangerous fevers, and there is no cure for the disease. It was not until the invention of the first vaccine by Edward Jenner in 1796 that smallpox began to retreat from humanity. Hearing the news that milkmaids who had caught cowpox were not infected with smallpox, the English doctor took fluid from cowpox (a bovine[i] version of smallpox with mild symptoms in people) blister and scratched it into the skin of James Phipps. James soon recovered, and a later injection of the variola virus[ii] didn’t cause any infection. Doctors around the world started applying the new method to smallpox and various other diseases, and the World Health Assembly declared the eradication of smallpox in 1980.

 

The Immune System

 

Types of Immunity

 

All vaccines, including the smallpox vaccine that Jenner invented, works by introducing the immune system a new pathogen[iii] and making it develop immunity towards the disease. In other words, vaccination affects the acquired immune system. There are two types of immunity that protects the body against infection. Innate[iv] immunity defends you from all kinds of germs, by keeping them from entering your body. Examples include the skin, mucus[v], stomach acid, etc. Unlike the innate immune system, the acquired immune system fights specific germs. It can be acquired by antibodies made after an exposure to infection or getting inoculated[vi] against a certain disease.

 

The Acquired Immune System

 

To make it simple, the acquired immune system consists of three leukocytes[vii]. Macrophages[viii] engulf and digest foreign cells, bacteria, and viruses. T-lymphocytes[ix] and B-lymphocytes, aka. T cells/B cells, kill infected cells, produce antibodies, and ‘remember’ the pathogen.

 

When a pathogen is introduced to the body, macrophages ‘eat’ the pathogen in a process called phagocytosis[x]. In the phagolysosome, a cytoplasmic body formed by the fusion of a phagosome[xi] with a lysosome[xii], the pathogen is broken down, and components of it are presented to a T cell by the macrophage. The helper T cell, having received information about a new pathogen by the receptor protein, activates cytotoxic T cells (killer T cells) and B-cells. Cytotoxic T cells kill infected body cells. Activated B cells produce the first specific antibodies against the antigen, and proliferates into plasma cells and memory cells. Plasma cells produce specific antibodies that surround the virus antigen and make antigen-antibody complexes, and memory cells remember the pathogen and can easily defend another attack from the same kind in the future.

 

Vaccines

 

Whole-Virus Vaccines

 

Whole-virus vaccines use inactivated or live-attenuated[xiii] viruses. Inactivated vaccines contain viruses whose genetic material has been destroyed so that they cannot replicate, but can still trigger immune responses. Live attenuated vaccines used weakened viruses that do infect body cells and duplicate, just like ordinary viruses. The difference is that infection by these weakened viruses causes only mild symptoms or cannot cause illness at all. The familiar influenza vaccine is an example of live-attenuated vaccines.

 

Subunit Vaccines

 

Subunit vaccines activate the immune system by introducing the body to parts of a pathogen. They do not present the whole pathogen, but instead present one or more antigens that are the fragments of the pathogen. Protein subunits are often used as the antigens in subunit vaccines. These kinds of vaccines for COVID-19 include the EpiVacCorona vaccine or the Novavax COVID-19 vaccine.

 

Genetic Vaccines

 

Genetic vaccines are vaccines that use the DNA or RNA of a virus to stimulate the acquired immune system. Hence, they are each called DNA vaccines and RNA vaccines. They are vaccines that carry DNA or RNA sequences that, once in a body cell, can produce antigens that trigger immune responses. DNA vaccines work by injecting genetically engineered plasmid containing the DNA sequence encoding the antigen. RNA vaccines work by the injection of mRNAs. Translation of a mRNA produces proteins such as the spike protein, with is presented to cells of the immune system. Pfizer-BioNTech and Moderna vaccines for COVID-19 are RNA vaccines. They are the first RNA vaccines to be approved and to be in use.

RNA vaccines (for COVID-19) don’t affect your DNA. mRNA are easily destroyed out of cells or after making a protein. It is also the reason why Pfizer vaccines have to be transported and stored in such low temperatures.

 

Viral Vector Vaccines

 

Viral vector vaccines use a viral vector to stimulate the immune system. They use a harmless virus as a delivery system for carrying part of the targeted virus’s (in this case the coronavirus’s) genetic code and presenting it to the immune system. Weakened viruses that are safe and well-studied are used as vectors. Replicating viral vector vaccines provoke a strong immune response by enabling the vector to multiply itself in host cells. On the other hand, non-replicating viral vector vaccines, which no vaccine is yet licensed with this method, introduce to the body a vector that cannot duplicate. Therefore, booster shots may be needed for long lasting immunity.

 

 

 

image source: https://en.wikipedia.org/wiki/Phagosome

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[i] bovine: related to cows

[ii] variola virus: the virus that causes smallpox

[iii] pathogen(병원체): a microorganism that can cause a disease

[iv] innate(선천적): inborn, natural

[v] mucus: 점액

[vi] inoculated: vaccinated

[vii] leukocyte: 백혈구

[viii] macrophage: 대식세포

[ix] lymphocyte: 림프구

[x] phagocytosis(식균 작용): the ingestion of bacteria or other material by phagocytes

[xi] phagosome: 포식 소체

[xii] lysosome(리소솜): a cell organism that contains digestive enzymes

[xiii] attenuated(약독화된, 감쇠된): having been reduced in force, effect, or value