Allergic to something? Many of us are. Whether it’s itchy earlobes from those not-so-expensive earrings from a not-so-missed ex-boyfriend, or wheeziness during the hayfever season, allergies can be a pain! But we can usually just get round it by avoiding what we’re allergic to, right? (or in case of hayfever, just taking some anti-histamines?).
But what if you’re allergic to yourself?
This is the basis of autoimmune diseases.
Quite simply, an autoimmune disease arises from your body’s immune system attacking itself, creating an internal civil war between your body’s normal defenses and the tissue it’s attacking! Because the target is yourself, you can’t simply avoid what’s causing the reaction, and common drugs like anti-histamines are largely ineffective.
Autoimmune diseases are surprisingly common, and their occurrence is rising! Here are a few examples of autoimmune disease, some of which you’ll have heard of, and some you probably haven’t!
Type One Diabetes: Body vs. Pancreas
Practically everyone has heard of diabetes, and quite a few people will know there are two distinct types. Type 2 diabetes (also known as late-onset diabetes) usually arises later in life, and is an autoimmune disease. Type 1 diabetes (also known as early-onset diabetes or insulin-dependent diabetes mellitus) arises early in life, and is the result of the body’s attack of the pancreatic beta cells, which are responsible for the production of insulin, the hormone responsible for regulating blood sugar levels. Because the resulting damage is irreversible, the ability to produce insulin is completely diminishes, and diabetes results from the inability to regulate blood sugar levels.
Systemic Lupus Erythematosus (SLE): Body versus … many things
Lupus, but it’s never lupus – right? Wrong. SLE is a very complex autoimmune disease that causes disease is a number of different organs, including the kidneys, skin and joints. The exact cause and molecular mechanisms of lupus are largely unknown, but one mechanisms of disease biology is thought to be production of antibodies against the body’s DNA. These antibodies then form immune complexes which are deposited at susceptible sites of the body (such as the skin, joints kidneys), giving rise to symptoms!
Multiple Sclerosis (MS): Body versus Brain
MS is a particularly nasty degenerative neurological condition, whereby the immune system targets and damages cells of the brain. The brain’s neurons are usually insulated with myelin to increase the efficiency of signalling, but in MS these insulting sheaths are damaged and signalling is interrupted – like stripping wires of their insulation. Inflammation associated with this damage also contributes to the manifestation of MS symptoms.
So why are autoimmune diseases on the increase?
One reason why we think autoimmune diseases are becoming more common is because we’re all living much cleaner lives! The idea is that because we’re not being challenged by dirt, bugs and slime on a daily basis our immune systems aren’t properly trained to tell the difference between friend (our own body’s tissues) and foe (invading bugs). This is just a theory at the minute, but we’re starting to accumulate some very convincing evidence!
How do we treat autoimmune disease?
Autoimmune disease is hard to treat. Reducing inflammation and suppressing the immune system are the main ways of treating, but for many diseases (like MS) there are very few effective therapies indeed. The absolute cause of autoimmune diseases is hard to identify, as patients only present with symptoms after the initialising event has occurred (many autoimmune disease can take a long time to manifest), and this lack of understanding of disease biology can make it very difficult to identify therapeutic strategies!
Immunosuppressants to down-regulate the immune response against ourselves also have their own associated risks – other than drug toxicity, opportunistic infections (where pathogenic bacteria and viruses take advantage of our lowered immune systems) are a big problem for patients undergoing such therapies.
So that’s a little something about autoimmune disease! It’s a very interesting and largely poorly-understood area, with a long way to go treatment-wise for many of these diseases.
DeGiorgio LA, Konstantinov KN, Lee SC, Hardin JA, Volpe BT, & Diamond B (2001). A subset of lupus anti-DNA antibodies cross-reacts with the NR2 glutamate receptor in systemic lupus erythematosus. Nature medicine, 7 (11), 1189-93 PMID: 11689882
Rook, G. (2011). Hygiene Hypothesis and Autoimmune Diseases Clinical Reviews in Allergy & Immunology, 42 (1), 5-15 DOI: 10.1007/s12016-011-8285-8
Loma, I., & Heyman, R. (2011). Multiple Sclerosis: Pathogenesis and Treatment Current Neuropharmacology, 9 (3), 409-416 DOI: 10.2174/157015911796557911
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