The human body is made up of many different kinds of cells. Some of these are quite underappreciated; others are pretty much disliked for what they do. Cells of the immune system protect us every single day from the microscopic world that is continually trying to eat away at our bodies. In this article, I will discuss the first part of the immune system, the one that is fairly mindless – the innate system.
Now, the innate system includes all the body defenses that do not have to be activated in order to work. This includes things like your skin, stomach acid, mucous (kind of disgusting, but there it is), and some very specialized cells. I will discuss those cells in further detail later on, but I want to focus on the first defensive barriers for now.
Now, think of your body as an impenetrable fortress. What would you picture? Walls 600 feet high? Stone 6 feet thick? If you made your fortress completely impenetrable, would you have things like doors or windows? Of course not – things can come in through doors and windows. Now, are doors necessary? Absolutely – how would you get out of your impenetrable fortress for things like food, water, clothing?
Our body works the exact same way, through our skin. Our skin is our major first-line defense against infection. Unfortunately, you have to have ways to eat, see, and eliminate wastes. So, you have doorways – entrances through your impenetrable barrier. These areas have their own defenses. Of course, if you get a cut, you’ve now made a new doorway, and nasty things can enter those as well.
Mucous secretions are next on the list. These include things like tears, ear wax, mucous in your lungs/throat, and, since I don’t want to use the medical term (keeping it simple), snot. Most of these things are not exactly pleasant, but here’s what happens. First, little creatures tend to get stuck in mucous. Several things can happen then – they can die immediately (you produce things in your mucous that can kill some creatures), or they get moved out of the body. I do say moved out – in some cases, those mucous secretions can enter your stomach, which is my next topic.
Your stomach has a ph of around 1.0-4.0, depending on when your last meal was. It rises to the 3.0-4.0 level after a meal; if you haven’t eaten in awhile, it can lower to about 1.0. Basically, what these mean is that your stomach is extremely acidic (a neutral ph is 7.0, lower is acidic, higher is basic (bleach)). Most creatures that you could ingest don’t really like acidic places, and so most of them die.
There are a couple exceptions to this. Some creatures actually like acidic places, and will set up shop in your stomach. Others will be ingested with food (think E. coli) and will hide in the center of the food particle. Most will be killed off, but some might still make it through the stomach, and the rest of the intestinal tract is around 7.0-8.0, which makes these creatures much happier – so happy in fact that they reproduce, set up shop, and make you very sick.
OK, so what happens if a creature gets past all of those defenses (and I’ve left out a couple, such as the creatures that already live in your gut)? We have certain types of cells that will attack them, without having to be told to do so.
It would be completely improper to introduce some of these cells, so I will do so. The first cells I would like to talk about would be what is called phagocytic cells. These cells basically eat other cells, ones that do not belong in the body. They are the hungry teenagers in your system – eating anything that they find that doesn’t belong. Some of these cells (types are macrophages, monocytes, and neutrophils) are important for what is called the acquired immune response, more on that in the next article.
Most of these eating-type cells contain lots of nasty chemicals, which they put with whatever they eat to kill it. There is really one exception to these cells, and they are the natural killer (NK) cells. These cells will kill your cells if they contain things like a virus, and some forms of cancer. Since most viruses live in “host” cells (your cells), this is the only way that your innate system has to kill them off.
Now, of course this is a simplified view of your first line of defense, and I’ve not talked about all the different things these cells can do, but this should give a good overview of this part of your immune system. Now, on to symptoms…
When your innate system is activated, it can cause things like inflammation, fever, runny nose, etc. Now, while these are all signs that you have an infection of some type, it is a completely normal response to any type of infection. OK, some infections do not cause fevers, but you get the point – these symptoms are common across a wide variety of infections. This is important to note, since these are signs that your innate immune system is functioning normally. I mentioned this in my last article on vaccinations.
Now, one last thing. Your innate system is only the first part of your immune system, but it is also the fastest. It takes very little time – minutes to hours – to become fully active against any threat. Now, the downside of this is that it reacts to any infection exactly the same each time – it has no memory of previous infections, and so it can’t do what is called a targeted response.
That type of response is a function of the acquired immune system, which I will discuss in my next article. That system takes days to be activated, but after it has seen something once, it can mount an immediate, targeted response.
Until next time – stay healthy!
***EDIT – I completely forgot to source my information! So sorry about that – my information is in Kuby Immunology, 6th edition, chapter 3 on the innate immune system. Book is by Kindt, Goldsby, and Osborne, published by W.H. Freeman and company, New York