Better know a Cytokine: IL-25 (formerly IL-17E)

First things first. IL = Interleukin.

Now that the housekeeping is out of the way, we can get down to business. I figured it would be best to start with the cytokine that really got me into this line of thinking about the fundamental components of the immune system that we don't really know or understand well yet. I was reading a recent article from the Journal of Allergy and Clinical Immunology, like I have been known to do, and it hit me. This IL-25 thing may be a huge key to a lot of things.

How did I get there? Well, the article in question is related to non-IgE mechanics for allergic inflammation and airway reactions. I was curious about this particular phenomenon because I have many friends who produce no IgE but yet manage to have severe allergic reactions to varied things. I decided to read the article, then got hooked. I read further articles and there are some interesting things that make IL-25 unique.

IL-25 was once thought to be in the IL-17 family of cytokines because of the way it has been demonstrated to differentiate the T helper 2 lymphocytes into different immunoglobulins. It has a distinct role from IL-17A and IL-17F which eventually led to a different taxonomy. Basically, it impacts a whole different cell set. The 17 family seems to generate a distinct type of T helper cell (Th17), while IL-25 doesn't.

IL-25 does seem to have something to do with the daily problems I experience, however, because of its relation to the inflammatory processes of the body. It causes inflammation in the skin tissues as well as in the airways of the lungs. It can exacerbate asthma symptoms. In my disease experience, the inflammation of my airways has been pretty inexplicable. The antibodies aren't there to produce the problems... perhaps it is my cytokines like IL-25 instead? Hard to say.

I discussed this with my doctor yesterday and he agreed that there is a strong possibility that the allergies shown in people with immune deficiencies could well be something related to IL-25. We already know that hyper IgE syndrome (another PIDD) is a cytokine-mediated problem. Basically, the cytokines don't regulate the IgE properly. We don't really understand much of this yet, but it's super fascinating.