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Immune system features cells in your body that work day and night together to protect you from a constant threat of pathogens that are constantly trying to bring mayhem. And most of the time, you don’t even know it. By pathogen, I could mean a lot of things, A line-up: Viruses. Bacteria. Fungi. Protists, parasitic worms. Your body has external protection against these things, like your skin. We call that a first line of defense because it’s the first line against letting these pathogens inside your body. Mucous membranes too, like the lining of your nose, will keep pathogens from getting inside. This first line of defense is non specific, because it’s not selective about what it blocks from getting into your body. But this is all not fool-proof, and sometimes they do get in, and when they do, your immune system has all kinds of ways to deal. After all, this is not its first rodeo.

So let’s say they break through our first line of defense. Well, the 2nd line of defense, includes the inflammatory response. To explain it very simply–let’s say you step on a sharp stick. And there’s some bacteria on that stick in your foot, The initial damage of this stick into your foot can cause certain types of cells, such as a mast cell, to react. These cells are filled with substances that work with allergic responses and inflammatory responses too. One substance that they contain is histamine. If they are triggered to release histamine, the result is that this will cause blood vessels to dilate—meaning they widen—near the injury. Histamine also contributes to making these blood vessels leakier. The dilation and the leakiness of the blood vessel makes it easier for many types of white blood cells such as certain types of macrophages to reach the area. And macrophages do what macrophages do best. They consume the pathogens. Additionally, your body has a complement system, The complement system is not what it sounds like, It basically works to help or complement the actions of the immune system. It can work with non-specific or specific responses. In this situation, the release of complement factors in this case can further attract macrophages to the area to consume pathogens. When all of this signaling stops, the damaged area can return to normal. The pathogen has been terminated. However, that also was a nonspecific response. Who knows what was on that stick? So that takes us to the 3rd line of defense. The specific line of defense. If you had a cold virus spreading throughout your body, you may need your response to be targeted on that pathogen. Now, as we give our typical notice, the immune system is very complex. We’ve just been giving some basics, and we’re going to continue to do so, but there are a lot of extra details and exceptions that we can’t go into. We encourage you to explore. Ok so we mentioned, what if we need a more targeted response?
Then we have to look into adaptive immunity, which would be continued in the next part.

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