One of the main components of our body, is the immunity system. Responsible for identifying and acting against diseases, the immunity system acts by detecting a "wide variety of agents, from viruses to parasitic worms, and needs to distinguish them from the organism's own healthy cells and tissues in order to function properly" (Wikipedia).
Before knowing how the system works, it is crucial for us to understand the causes for such functioning. Our immunity acts against pathogens, which are any living organisms or viruses capable of causing diseases. Some examples of pathogens are bacteria, viruses, fungi, protists and worms. (Photo: bacteria E Coli)
Taking into account bacteria, we can also start comparing the use of antibiotics when treating bacteria itself, and viruses. While antibiotics are effective against bacteria, they are not against viruses. This is due to their structures and normal functions. For example, bacteria are prokaryotic cells, therefore, they have a metabolism and a cell wall. Antibiotics act by blocking such metabolic pathways found in bacteria. Viruses on the other hand, are not cells, given that they are made of only a capsid and nucleic acid. Also, seeing they don't have it, viruses reproduce using the host cell's metabolic pathways, which are not affected by antibiotics, given that they are from our own body.
So how does the immunity system work?
To start up with, the immunity system is something that takes place even if we do not realize it is actually helping us. Starting with our first lines of defense, the process of immunity and avoiding pathogens within our body already takes place in our skin. Our skin is made of two layers; epidermis and dermis, the first one being impermeable, having a lower pH and already having other bacteria in it, which prevents other ones from growing. If such mechanism still fails, chemical secretions such as mucus, trap and kill microbes.
This second line of defense contains anti-bacterial organelles such as lysosomes are also present in mucous membranes, which further helps the body defense against pathogens. Phagocytic leucocytes, also known as macrophages, are present in the mucus, and help by ingesting large white blood cells that engulf pathogens. Finally, mucus, also helps when cilia sweep it back to the throat, leading germs to go to stomach to get destroyed by the acid environment.
Additionally, the immune system is also composed of antibodies and antigens. Antigens are substances, macromolecules that provoke an immune response through lymphocytes. On the other hand, antibodies are proteins secreted by plasma cells that bind to an antigen, recognize it and marks it for elimination. Antibodies are made by lymphocytes, which recognize an enormous number of antigens, but each individual cell recognizes only one type of antigen. Each lymphocyte puts some of the antibody that it makes into its cell surface with the antigen-combining site projecting outwards. Antibody production starts when a pathogen enters the body, its antigens bind to the antibodies in the cell surface of one type of lymphocyte (macrophages engulf it). Then the antigen is incorporated to macrophage membrane, which will be presented to helper T-cells. These helper T-cells then bind to the antigen located on the macrophage, and immediately activate T-cells, which will activate B-cells. Seeing that antibodies are produced in response to specific antigens, they will be made by B or plasma cells; they will be B-cells clones. Such clones will later spread into plasma cells and memory cells, the first one producing specific antibodies to the specific antigen. Some of the cells develop into short-lived plasma cells that secrete antibody specific for the antigen. Others develop into long-lived memory cells that can respond rapidly upon subsequent exposure to the same antigen.
Finally, the issues that IB most relates to the immune system is AIDS, caused by the HIV virus. HIV became really popular due to its easy transmission. It involves the transfer of body fluids, such as blood, placenta, or milk from breast feading, from an infected person to an uninfected one. HIV can also be sexually transmitted, or from the use of contaminated needles, or blood transfusions. Additionally, the problem of AIDS is not merely the virus itself, but also the implications involved in such. Individuals infected with HIV may not find partners, housing or employment. Also, reproduction activity in a population may be reduced because of the fear of AIDS, and families may become poorer if the individual with AIDS was the wage earner and is refused life insurance. As I have already watched it, I would highly recommend everyone to watch the movie Philadelphia, click here to see the trailer, given that it gives a fair and new insight in the life of a person who is affected by the virus and how it has changed his life.
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