Hey! If anyone has the time to read all this and correct me that would mean a lot! This is for my biology project about the immune system. Also to tell me where i need more explanations. If it isn't too much of a hassle could you mark me out of five for the following:
1.Knowledge of the structure and function of the immune response.
2.Evaluation of the similarities and differences of the non-specific and specific immune response
3.Understanding of the concept of self and non-self
4.Application of the knowledge of the immune system to on particular aspect of the immune response(Allergic reaction)
5.Communication of knowledge and understanding to the intended audience(Yr 12 students)
Thanks!
Introduction:
The immune system is widely regarded to consist of three lines of defense: The first line of defense, which acts as barriers for the pathogens. If the first line of defense has been compromised, the second line of defense is activated. The cells involved in the second line of defense will attack any foreign material, hence non-specific. If the pathogen has not been neutralized, the specific immune response will occur, also known as the thirld line of defense. We will look at how these lines of defenses protect us from pathogens.
First line: The first line of defense acts as barriers for the pathogens. The best way to not get infected is to not let pathogens in after all! The first line of defense include: intact skin, which itself prevents pathogens from entering body tissue. Mucus in respiratory tracts, mucus is a sticky liquid that contains the protein mucin. Since it is sticky, pathogens will get stuck in it and the cilia of the mucus membranes will beat upwards, pushing the mucus to the throat ultimately swallowing it. Where it will be destroyed in the stomach, the stomach contains hydrochloric acid which is very low pH, most pathogens or microbes in general will be destroyed when they come into contact with this acid. Natural flora of your body that is found in gastrointestinal tracts and on your skin are non-pathogenic bacteria, the normal flora prevents pathogens from reproducing into large numbers, since they will have to compete for resources. Sebum which is an oily substance secreted by sebaceous glans and hair on your skin provides an unfavorable environment to pathogens. Since the skin is mainly comprised of dead cells, it is already hard enough to penetrate the skin unless it was damaged but your eyes and mouth are made of living cells, making them prone for infection. So an enzyme called lysozyme is present in saliva and tears. This enzyme catalyses the lysis of pathogens(causing them to explode).
Second line:
If the first line of defense could not prevent the pathogens from entering the body, the second line of defense is activated. The second line of defense includes phagocytes, mast cells and natural killer cells. Macrophages, dendritic cells and mast cells tend to stay around skin cells(since they're close to the external environment). Any pathogen that infiltrates the body will most likely come into contact with these cells. Dendritic cells and macrophages are what we call Antigen Presenting Cells(APC) meaning that when they engulf an antigen by phagocytosis they will process it and then present it on their MHC class 2 markers on their surface, this is important for Th cells(which is part of the specific immune response). Mast cells contain a chemical called histamine, when this chemical is secreted it vasodilates blood vessels allowing more blood and fluid to the area(this is why your skin goes red when infected) which also allows neutrophils and monocytes to emigrate into the area to assist in the fight against the pathogens.
Third line of defence:
The third line or commonly knows as the specific immune response contain lymphocytes(B-cells and T-cells). B-cells all have different antibodies but all those different antibodies can only bind to one antigen that is specific for that antibody, hence specific immune response. B-cells bind to their specific antigen which will activate them, stimulating the B-cell to proliferate and differentiate into two types: 1, memory B-cell(Same as the parent cell but lasts for a long time) or into plasma cells, which produce and secrete antibodies for the specific antigen, T helper cells only bind to antigens presented on MHC class 2 markers, this activates the T-helper cells stimulating it to proliferate and differentiate into two-different cells:1. Memory T helper cell(same as parent cell) and effector T helper cells. The effector T cells release cytokines(signalling molecules for cells of the immune system).
Self/non-self
Cells are recognized by the receptors present on their surface.
Similarities/differences:
Innate immune response-Does not discriminate against antigens of pathogens, it will try to keep all pathogens from entering the body and will attack all pathogens that enter the body.
Active immune response- Has memory cells(cells that are the same as the parent cell, but lasts for a long time). Different receptors for different antigens, only specific antibodies will bind to specific antigens.
Allergic response:
Also known as hypersensitivity class 1
When an individula is infected by an allergen for the first time, plasma cells will produce and secret igE antibodies, which bind to mast cells to be used as receptors. The second time an allergen infects the body, the allergen will bind to the antibody, initiating the mast cells to release all of the granules of histamine present in it. Histamine irritates pain sensory receptors(which is responsible for itching). Histamine vasodilates blood vessels, allowing blood and fluid to enter the tissue(this is why your skin goes red). Histamine constricts respiratory tracts(which is responsible for individuals having difficulty breathing)
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