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Problem/Question: What happens when germs and diseases enter your body? Where do they go? What do they do? And most importantly, How are they dealt with by the body, and specifically the immune system.
Our body rejects pathogens ( which are microorganisms that cause diseases). When they enter our body they are taken care of by our immune system which is like our bodies defense system. It destroys these pathogens through three different defense layers called the 3 lines of defense.
This flow chart will explain the process in which the pathogens go through until they are killed.
The antibody molecules bind to any antigen similarly to how a substrate binds with an enzyme except not as precisely. The better they fit together, the better the following immune response will be.
By combining, the antigen labels the pathogen as foreign.
Lots of the time, the antibodies will combine with the plasma cells so that a really complicated mass is made. The pathogens clumping together make themselves venerable to phagocytes. The antibodies, when stuck to bacteria, make the bacteria more recognizable for the phagocytes. Also the antigens acting as toxins in the body will be neutralized with an antibody with it, so the antibodies will be acting as an antitoxin. A virus with an antibody can't attach to or enter a host cell anymore.
Germs are everywhere, lots germs are bad for us but some germs are good for us and help make stuff like enamel. Pathogens are also types of germs that cause diseases. The types of pathogens are bacteria, viruses, toxins, parasites, and fungi. Our body doesn't want diseases and so it fight back with a complicated system of defenses. There are three lines of defense. The first one is our surface defense which is basically a non-specific defense which includes physical and chemical defenses and parts of our body like our skin and mucus membranes. Our second defense is innate immunity which is a 3 step attack that occurs if the pathogens survive the first defense, it is also non-specific. The third and final defense system is more specific and complicated, it depends on lymphocytes.
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The First defense is non-specific, meaning it has the same response for all pathogens. It uses physical and chemical barriers and is always ready. The parts defending in the first line defense are skin, tears, mucus, cilia, stomach acid, urine flow, "friendly" or good bacteria, and white blood cells called Neutrophils.
Microorganisms can't get through your skin unless it is broken. So for them, your eyes, mouth and nose are perfect entries, but your tears, mucus and saliva all have enzymes that break down the cell wall of bacteria, if they don't die, they are caught inside the mucus and are swallowed and killed by the stomach acid. Cilia is thin hair lining your windpipe that keep particles ( and pathogens) away from your lungs ( which also has mucus just incase) and urine flow flushes out pathogens through your bladder. Good bacteria grows on your skin bowel and other parts of your body. Neutrophils search for pathogens, kills them and absorbs them.
The third response is quite powerful but still has a few flaws. For example you can't have an organ transplant because the immune system will recognize it a s foreign matter ( as it is not your own cells) and will be forcefully attacked and could be destroyed. the only was around this problem is to destroy the T-cells with X-rays and immuno suppressant drugs. There will be fewer T-cells but because of this they are now more vulnerable to diseases that wouldn't normally kill. Hopefully the pathogens will be destroyed by this defense line.
The second response system of the third line defense is the Humoral response. ( Just like T-cells) B-cells form a clone of themselves if they come into contact with a complemantary shaped antigen. the clone is made out of mostly plasma ( for immediate use) and some memory cells for for use in the future.
The plasma cells are highly developed and are able to create several thousands of antibody molecules every second. Unlike T-cells, B-cells do not have lymph nodes, only the protein ( antibody) molecules that they make move around the body. These proteins are released into the blood and carried to the site of the infection. They will be the right shape to bind with any appropriate antigen they meet except the one that caused the B-cells to be stimulated in the first place.
The second line of defense is called The Innate Immunity. It is only activated if the pathogens have survived the first defense. It is also non-specific, slightly more complicated and is a three step attack.
Inflammation is the first sign that's telling you that your immune system is doing what it's supposed to. That's good.
the infected area becomes inflamed because more blood is rushing there carrying with it, more white blood cells . The tissues will be a little painful, because they are filled with blood. the blood is also carrying heat with itself making the area look more HOT and red.
Different cells have different receptors molecules on their surface. When an antigen invades the body, macrophages present the antigens to the lymphocytes. When an antigen is shown to a T-cell ( which is a lymphocyte) in a complimentary shaped receptor, the T-cell is stimulated and increases in size and starts to divide. An identical clone is formed with the exact receptors, these T-cells are separated into four groups of specialized T-cells. There are killer T-cells, helper T-cellls, suppressor T-cells, memory T-cells. These guys ( except memory T-cells) then go to the site of the infection.
What do the ( now divided into four) T-cells do now?
When memory cells are created for a specific type of disease, that disease you can now become immune to that disease ( as in that disease can be taken care of really quickly and easily making it appear as though you didn't even have it!). Some diseases are like the cold, each time you catch it, the symtoms are always similar but every new cold is actually caused by slightly different viruses and antigens. Viruses have a high mutation rate, they may alter their antigens and even the slightest alteration means that the response will be as slow and hard as the first time ( because the memory cells won't recognize it).
By taking a vaccine means immunity can be artificially achieved by making you catch a disease ( that may have been altered or weakened to lessen it's risks) so that you can create the nessasary memory cells to combact this disease easily when/ if you ever catch it
The suppressor T-cells watch the immune system so when the antigens are dealt with, they can switch the immune system off.
Helper T-cells: Cooperate with B-cells in antibody production. Also activate macrophages and promote inflammation.
B-cells, in the Humoral response,create clones that are made of mostly plasma which can create several thousand of antibodies. Helper T-cells also help by creating many antibodies.
The memory T-cells stay there until after the pathogens are killed. To stop re-infection.
T-cells and B-cells all die out really quickly, they only live about a few days, memory B-cells and a few memory T-cells survive. The plasma cells and the memory T-cells only respond to antigens that they have previously encountered,so they wait for a re-infection. That way the secondary response is a lot faster and stronger.
Killer T-cells: Combine with antigens on the surface of any invading cell and release a powerful group of chemicals called Lymphokins. Some kill pathogens directly, others increase the inflammation so that there are more macrophages.
Even though the second line of defense it quite powerful there are still a few weaknesses to it. For one thing they can't deal completely with any one particular type of microorganism ( The response is the same for all types of pathogens so some different/ powerful ones may survive). Also it cannot remember past infections so a re- infection will take just as long as the first time to get rid of.
If this line succeeds in killing the pathogens, then stop here. But if they survive this defense then proceed to the third line.
There are three types of white blood cells: Neutrophils, Macrophages ( both are phagocytes which are are engulfing cells), and lymphocytes. Both types of phagocytes will engulf and digest the bacteria. Lysosomes are vesicles containing digestive enzymes. Pus is basically millions of dead immune cells which have already engufed the phagocytes ( which it was supposed to do).
-Pathogens: a bacteria, virus or other microorganism that causes disease
- Antigen: A toxic or foreign substance that causes the the immune system to respond my creating antibodies that will fight against it
-microorganisms: a microscopic organism, especially a virus, bacterium, or fungus
-antibodies: a blood protein produced in response to and counteracting a specific antigen
-infection: a disease or virus, the state of being infected
This defense depends on lymphocytes, the two basic types of lymphocytes called T-cells and B-cells. and are both made in the bone marrow ( which is found in cavities in the middle of bones). T-cells mature after their migration from the bone marrow to the thymus gland ( found between your lungs, behind your sternum), B-cells migrate and either mature in the bone marrow, the foetal liver or spleen. Once they mature they hunt for foreign antigens around the body. T-cells are mostly involved in the cell mediated process while the B-cells are mostly involved in the humoral response. These are the two different processes that the third line of defense is split into.
Macrophages make proteins that act in two ways. They can punch holes in bacteria and parasites, killing them. Or they can stick to the outside of a bacteria to make them look more appealing for the phagocytes to eat.
If a virus or a parasite that lives inside a cell ( intracellular parasite) has entered a cell, that cell will start creating a chemical called interferon. Interferon overall prevents that cell from creating molecules that the pathogens need to survive.