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B3 E) Fighting Diseases – The Immune System
B3 E) Fighting Diseases – The Immune System
There are many different ways that our body deals with pathogens. All of these different ways fall into two broad categories; prevention and the immune system. We looked at prevention in the previous section and we are going to look at the immune system response in this section.
Sometimes harmful pathogens are able to enter the body despite all of the preventative actions that the body takes. When this happens, the body’s immune system will respond to deal with the pathogen. White blood cells are the main type of cell that are responsible for dealing with harmful pathogens. White blood cells are found in the bloodstream. There are two different types of white blood cells; phagocytes and B-lymphocytes. Also, there are three different ways that our white blood cells deal with pathogens; here are those ways.
Sometimes harmful pathogens are able to enter the body despite all of the preventative actions that the body takes. When this happens, the body’s immune system will respond to deal with the pathogen. White blood cells are the main type of cell that are responsible for dealing with harmful pathogens. White blood cells are found in the bloodstream. There are two different types of white blood cells; phagocytes and B-lymphocytes. Also, there are three different ways that our white blood cells deal with pathogens; here are those ways.
1) Consume Them
Phagocytes can deal with pathogens by engulfing them and then digesting them. The phagocytes surround the pathogen. They then secrete some enzymes which breaks down/ digests the pathogen. The pathogen is then destroyed and therefore cannot do anymore harm. This process is known as phagocytosis.
Phagocytes can deal with pathogens by engulfing them and then digesting them. The phagocytes surround the pathogen. They then secrete some enzymes which breaks down/ digests the pathogen. The pathogen is then destroyed and therefore cannot do anymore harm. This process is known as phagocytosis.
2) Produce Antibodies
All pathogens have unique proteins on the outside of their cells. These unique proteins are known as antigens, and different pathogens have different antigens.
All pathogens have unique proteins on the outside of their cells. These unique proteins are known as antigens, and different pathogens have different antigens.
The B-lymphocytes travel around the bloodstream looking for cells that have foreign antigens (antigens that are different to the antigens on our own cells). When the B-lymphocytes come across a foreign antigen, they bind to it and start producing a protein called antibodies. The antibodies that are produced bind to the antigens on the pathogens, which causes the pathogens to clump together. The clumping together of pathogens makes the pathogens inactive and makes it easier for the phagocytes to engulf and digest the pathogens. The antibodies that are produced will be specific to the pathogen that they have been made for. This is because all pathogens will have different antigens, and each antibody will only bind to one specific antigen (we will look at this in a bit more detail later). As soon as the B-lymphocyte has created the correct antibody, they produce antibodies extremely quickly. These antibodies travel around the bloodstream binding to the antigens of the pathogen that they have been created for.
After your immune system has fought off the pathogen, some of the B-lymphocytes will develop into memory cells. Memory cells remain in the body for many years and sometimes a lifetime. Memory cells are responsible for making an individual immune to a specific pathogen. When the same pathogen enters the body, the memory B-lymphocytes start to produce the correct antibody extremely quickly. This is known as the secondary immune response (the primary immune response is the B-lymphocytes dealing with a new pathogen entering the body). The secondary immune response produces antibodies at a significantly greater rate than the primary immune response. This means that the secondary immune response usually gets rid of the pathogen before the individual experiences any symptoms. The graph below shows the levels of antibodies in blood during the primary and secondary immune response. You can see from the graph that there is a greater rate of antibody production in the secondary immune response compared to the primary immune response.
The two slashes on the x axis (/ /) show that there is a gap between the first time and second time that the pathogen invades the body. This gap could be a few months or a few years. Providing that the memory B-lymphocytes are still in the body, the secondary immune response will be what is shown on the above graph.
Only Immune to that Pathogen
Like I mentioned earlier, different types of pathogens have different antigens (proteins on the surface of their cells). The B-lymphocytes then produce antibodies that bind to the antigens on the pathogen. The antibodies produced are specific for that particular pathogen; they will only bind to the antigens on that particular pathogen and not all pathogens. For example, there are two pathogens below; A has square antigens and B has circular antigens.
Only Immune to that Pathogen
Like I mentioned earlier, different types of pathogens have different antigens (proteins on the surface of their cells). The B-lymphocytes then produce antibodies that bind to the antigens on the pathogen. The antibodies produced are specific for that particular pathogen; they will only bind to the antigens on that particular pathogen and not all pathogens. For example, there are two pathogens below; A has square antigens and B has circular antigens.
From the above diagram, you can see that the antibodies produced for A are square-like and will therefore only bind to the antigens on pathogen A. And, the antibodies produced for B are circle-like and will therefore only bind to the antigens on pathogen B.
3) Produce Antitoxins
Some pathogens like bacteria produced toxins. The immune system can produce antitoxins to counteract the toxins that the pathogen produces.
Some pathogens like bacteria produced toxins. The immune system can produce antitoxins to counteract the toxins that the pathogen produces.