What is an autoimmune disease/disorder?

From: http://www.beatricebiologist.com/2014/05/autoimmune/

Two weeks ago I introduced to you some of the cells in the immune system. As I mentioned, these cells can identify if there is something foreign (a pathogen or another particle) that has entered our bodies and, after this recognition, can proceed to respond appropriately. This of course implies that our body, and more specifically, our immune system can recognize our own body from other. But what happens when the immune system cannot tell who should and who shouldn’t be around?

In very simple terms, an autoimmunity disease is the result of our immune system no longer recognizing our own body and then attacking it. When someone gets an organ transplant, one of the things that makes this so hard is that you have to find as close a match as possible so your immune system doesn’t attack it. Even with the best match possible, transplant patients have to undergo medical treatment to “distract” the immune system until it no longer registers this organ as new/foreign. Now imagine that a part, or parts, of yourself are being considered as foreign ALL the time. This would be an autoimmune disease.

You may ask, why then don’t we just treat this disease with the same medicine transplant recipients are treated with? Because sure, this could lower the attack of your immune system upon yourself, but this also lowers the response to actual infections. So you see, it is not as simple.

Autoimmune diseases can happen all over your body, in a particular area (Rheumatoid arthritis for example being located in joints) or affecting several systems at a time (Systemic lupus erythematosus commonly known as just Lupus for example, affects several internal organs). Because autoimmune diseases can vary so much, in how and where do they affect the body, it has been suggested to talk mostly about autoimmune disorders and consider them as a spectrum.

There are several ways an individual might develop an autoimmune disease, including genetic (such as Multiple Sclerosis) and environmental factors. In the latter case, exposure to other factors including bacterial or viral infection causes a normal immune response at first, which can then get out of hand if part of the pathogen looks a little too much like a part of our body: this is called molecular mimicry. I feel that it’s important to clarify that in the case of genetic factors, a person carrying a determined gene will have a predisposition to develop the disease but might never actually have it. Also, in some cases of environmental triggered autoimmune diseases, when the environmental factor is removed (say, the bacterial infection is cleared) the autoimmune response might disappear as well.

I hope this has simplified the concept of autoimmune diseases. If you have any more specific questions or you would like a follow up, please let me know in the comments. In the meantime, have a lovely week and keep doing good science.

Meet the Cells of the Immune System

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A couple of weeks ago I talked to you about my project. However, it was (rightly) pointed out that maybe I should introduce the parts of the project little by little. So let's start with the cells I work with.

First a quick introduction. Our immune system (IS) includes not only cells, but also tissues and molecules that allow the system to recognize and respond to disease from the common cold (a viral infection) to tuberculosis (a bacterial one). Now, the IS can be divided in two: the innate and the adaptive system. The first one, also known as the non-specific system, can be found pretty much on any animal. Plants and fungus also have similar innate system. However, only beginning with jawed fishes (unlike lampreys for example) and going to the rest of vertebrates, have what it's known as adaptive immune system. The main difference is that, as the name implies, the second one is capable of discriminating the type of ailment that the organism is encountering and respond accordingly, whereas the innate will just attack anything that is foreign. Another cool feature about the adaptive system is immune memory: it will remember encountering a certain type of infection and that is how next time you get a similar infection, your body will be able to respond faster and more efficiently.

Today I will only talk about the cells involved in the innate system, mainly because the cells that I work with are part of it. But if you guys are interested I will talk about the cells of the adaptive system later on. For now we are going to talk about Mast Cells, Natural Killer Cells, Granulocytes and the cells I work with, Phagocytes.

Mast Cells are mostly known for their roles in allergies. Yeap, these buddies produce histamine, a molecule that is involved in inflammation (which causes the inflammation of sinuses, hence the stuffy nose, watery eyes, etc). But don't be mad at them. This same inflammation is important to call more cells to the infection cells (more troops to respond!) and in this way regulate the response to the infection.

Natural Killer cells (NK) have a very appropriate name. They are ready to destroy cells that have been infected, when said cells cannot defend themselves. They also produce a molecule that serve as a calling signal for the macrophages to come fight!

Granulocytes receive their name because when seen with a microscope you can see tiny dots (granules) in them. There are divided in two main groups: basophil, with very low numbers and just like the mast cell, contains histamine hence also having a say in your allergic reactions and inflammation; and eosinophils, who play a big role in the elimination of worm infections, but they will also participate in allergies.

Finally the phagocytes, cells that eat or rather engulf. They can ingest other cells (a dying cell for example), parasites and particles. They all have the ability of extending their membranes, like a reaching hand, to grab their target and get it inside them. We mostly talk about 3 main phagocytes: Neutrophils, believed to be the one of the first cell types to arrive to an infection site and triggering the response; then we have dendritic cells (DC), this beautiful cells that look a bit like and octopus or a medusa with long "arms", their main role is to present fragments of whatever was engulfed (parasite or dying cell) to let other cells around what type of action should be taken; and last but not least "my" cell, the macrophage: now these fellas can internalize several parasites at a time, or large particles which is why they got the "macro" part. Once inside, the internalized item will be "digested" to be presented, just like I mentioned DC do. Together DC and macrophages are also known as Professional Antigen Presenting cells.

That ends our little introduction to innate immune cells. Please let me know in the comments if it was clear, if you want more information on each cell, or anything you feel like sharing really. Next week, we will talk about proteins!