** Originally posted by DottieD **
A lot of research has been done on psoriasis, mostly dealing with studies of the lesions or with the inflammatory chemicals (like TNF-alpha or interleukins) that promote lesion development. There is also plenty of basic research on the immune system and inflammation. If some of this basic research could be connected to psoriasis, we would have a better understanding of the causes of psoriasis, and better able to do something about it. This post discusses one important connection.
Psoriasis is an immune system disorder. Because of our genetic makeup we are prone to develop inflammation in our bodies, causing an inappropriate reaction in our skin and sometimes joints. The reaction may be more severe if we eat a lot of sugar, gain weight, are under a lot of stress, or irritate our skin. We can sometimes reduce this inflammation by taking medications, moisturizing, eating less arachidonic acid, taking supplements, or doing UV light treatments.
BUT WHAT IS THE BASIC CAUSE OF THIS INFLAMMATION? WHAT GETS THE PROCESS GOING IN THE FIRST PLACE?
A lot of people with p have reported that they have an inflammatory reaction to certain foods, most frequently wheat, dairy, legumes (beans), or nightshade plants. I had a bad flare after eating baked beans last summer and also had a massive breakout after eating wheat germ a number of years ago. These foods were causing a FOOD INTOLERANCE (also called a food sensitivity), and I have learned that something called lectins are responsible.
I have been studying exactly what happens when intolerance occurs – to see if this would shed light on how some of us develop psoriasis and why it sticks around. Here is my understanding from what I have read:
Our bodies’ cells have protein-sugar molecules sticking out on their surface. They are called SURFACE RECEPTORS and we are all unique in the exact structure of these molecules. (Please note that there are a lot of different types of sugars other than what we call “sugar.” The ones involved here are other members of the sugar family.) LECTINS are a class of proteins that bind to the sugar part of these surface molecules, but only if the structure is a perfect match – much like a key that fits a certain lock. Our bodies produce natural lectins that perform many functions, such as antibody actions. But we also eat a lot of lectins that come from plants. And some of these can cause a bad reaction in our body.
Our stomach and small intestine walls are lined with epithelial (skin) cells and some cells that secrete mucus. Like other body cells, they have surface receptors.
When proteins are digested, they are supposed to be broken down into amino acids before entering the body – either as single units or at most chains of 2 or 3. That way, the body can make the exact proteins it needs. Also, this prevents foreign proteins (as in viruses) from gaining a foothold. Our white cells are constantly on the lookout for foreign proteins and foreign surface receptors, and will go to work immediately to try to get rid of any they come across – this is part of the inflammation reaction.
Suppose you have an intolerance to some type of lectin (such as gluten). Here is what is thought to happen when you eat it:
First, some of the lectin may attach to surface receptors in the stomach. This binding causes a decrease in mucus secretion which may result in overgrowth of bacteria in the stomach. The lectin attachments cause an inflammatory response in the stomach wall, causing it to secrete more histamine, which in turn stimulates more acid secretion. The person may feel heartburn.
Secondly, lectins are very resistant to being digested, so when they get into the small intestine they don’t break down into amino acids like other proteins. If you have an intolerance to the lectin, you have exactly the right “lock” on the cells lining your gut wall for the lectin “key”, so the lectin proteins attach to the gut wall. This binding causes disruption of the normal wall activity: the epithelial cells are stimulated to wrap their cell membranes around the lectin proteins and move them into the small intestine tissue (a process called exocytosis). Once in the gut tissue, the lectins cause an inflammatory response from the white cells residing there. In addition, part of this lectin moves on into your body circulation where it can cause damage to your body.
If you continue to eat the offending lectin day after day, month after month, the intestine walls gradually become more inflamed. They are stimulated to grow and divide more, causing disruption of the normal tight bonding between the cells; the intestine wall becomes more irregular and defective areas gradually develop. At some point these defects may become large enough for other proteins or protein fragments to leak through. These proteins may cause their own problems in the body (particularly in joints, brain, and skin), and the white cells and the liver have to work hard to rid the body of them.
The story is actually a little more complex, but this additional info explains why strep or other respiratory infections often cause psoriasis to develop or worsen. The following is a summary from an article by Dr. David Freed in the British Medical Journal (1999):
The tips of the protein-sugar molecules sticking out of our cells are normally covered with a fine screen of sialic acid molecules. Sialic acid is another member of the sugar family. Inside our body, this coating of sialic acid protects the surface receptors from unwanted lectin attachments and helps keep the cells hydrated. Strep bacteria and several other infectious germs are able to strip the sialic acid off the receptor tips when they invade the body. Thus, these receptors are now available for lectin attachment. The binding to lectins can disrupt the function of that tissue. It also causes white cells to attack the tissue - which is called an autoimmune response.
Another article explained that strep bacteria make their own lectins, and after stripping away the sialic acid, may use these lectins to attach to our cells.
To be Continued: What can be done to solve this problem.