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Introduction to Immunology

Immunology is the study of cells, organs, and chemical components of the immune system. A human immune system recognizes “self” from “non-self” and neutralizes the microbes if attacked. A much faster and effective response is released if attacked again. This memory response has been mentioned throughout history.

Back in the time of plague, Thucydides wrote that people who have been exposed to the plague could care for the sick without the fear of being infected again. Edward Jenner later went on to be the first to find a vaccine for smallpox back in 1978. Although he successfully invented a vaccine, he was not able to explain the concept of how immunity develops. It was Louis Pasteur that introduced the concept that vaccination could be used for any microbial disease. Pasteur’s pioneering work in immunology, termed him the father of immunology.

Louis Pasteur

Initial barriers:

Microorganisms or pathogens can enter the body at different sites and produce symptoms by various mechanisms. When microbes attack the body, they first need to go through initial barriers. A human body’s first immune barriers are physical for example skin. It is usually enhanced by secreted substances like tears and saliva that have the potential to neutralize the microbes. 

Even the barriers inside the body also called mucosal tissues (eg. lungs and the gut) are coated with mucus to trap any sort of pathogens. In the case of airways, ciliate hair works in steering away contaminants from the body’s vulnerable areas. These barriers are also heavily populated with immune cells that are ready to respond to microbes that breach the initial barriers. 

Immune organs/tissues:

There are many organs and tissues that work together to defend the body against microbes. The organs and tissues of the immune system are divided into primary lymphoid organs and secondary lymphoid organs. 

Primary lymphoid organs:

The primary parts of the immune system include, bone marrow, and thymus. Bone marrow (BM) is where all the body’s blood cells originate. While B lymphocytes stay in BM to mature, the T cells travel to the thymus. 

The thymus is a bilobed area located above the heart. The thymus slowly starts to shrink and is replaced by fat and connective tissues after puberty. The lymphoid organ is also responsible for producing thymosin, a hormone that aids in the production of T cells. The thymus will have produced all the necessary T cells by the time of puberty. 

Secondary lymphoid organs:

Once the T and B cells have matured in the thymus and BM, they travel to the secondary lymphoid organs, spleen, and lymph nodes, where they remain till called for. Lymph nodes are located throughout the body, and the spleen is located in the upper left area of the abdomen. The main function of the spleen is to filter the blood, where the red blood cells easily pass through. The damaged blood cells are detected and broken down and engulfed by the immune cells in the spleen. 

In addition to the spleen and lymph nodes, gut-associated lymphoid tissues (GALT) and mucosal-associated lymphoid tissue (MALTs) play an important role in the immune system. MALT is usually found in areas containing mucous such as the skin, nose, eye, and mouth. They usually contain the immune cells that are usually defend against pathogens trying to enter from outside the body. GALT is a lymphoid tissue usually found in the mucosal and submucosal areas such as the appendix, and Peyer’s patch in the small intestine.

Stay Tuned….

Hope this detailed introduction has given you the much-needed knowledge on the basics of Immunology. Stay tuned to The scientific reporter for all information on immunology. The next stop in this informative series is a detailed explanation of innate (non specific) and adaptive (specific) immunity.



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