So I have some pretty severe allergies. Given the wide variety that I have personally I would be surprised if science found a single mechanism that caused all allergies. But I have to admit, I never thought that the fact that I am not, nor have I ever been, exposed to parasites would be at fault for even a few of my allergies.
A new study compared proteins that are known to cause allergies with proteins from different species of parasites. They found a list of 2445 parasite proteins that are very similar to those in different allergens. It turns out that this is actually a known mechanism, but this study was the first systematic look. So rather than looking at one or two parasites and one or two allergens, they looked at 2712 allergens and 70,000 proteins from 31 species of parasites. Does that mean that we’d find more similarities if we looked at more parasites? Potentially.
Allergies are a strange beast. If you think of any of the kids toys where you have to match a particular object with a hole that has the same shape you have an idea of how allergies work. Just switch out the hole for a virus, bacteria, or parasite. They have particular shapes that match specific antibodies produced by your body. If they find a match, the antibodies will bind to the invader and set off an immune response to protect the body. Unfortunately, just like different people may be mistaken for each other based on their appearance, sometimes the antibody will bind to a different item like a peanut protein, mistaking it for a dangerous invader. When this happens, you still get the immune response but your body isn’t protecting you from anything that is actually dangerous.
In extreme allergies the immune response itself is life threatening. So like so many good ideas, this one is flawed in its execution.
So, can this connection to parasites explain why my friend from Africa had never heard of a peanut allergy until she came to North America? Consider a wanted poster that you see on tv. If you saw the person in the poster immediately afterwards you would probably recognize them. But what if you saw the person a week later. Or what if you saw someone who looked really similar, would you know for sure that they were or were not the right person? If that individual was responsible for a horrible crime would you wait to find out if it was the correct person, or would you call the cops just in case?
This is what happens with allergies that are connected to parasites. My body doesn’t see a lot of parasites so it can’t remember exactly what they look like. It thinks however, that the peanut protein is pretty similar so it’s better to be safe that sorry right? Call out the swat team and eyes swell up, breathing stops, all in all it’s pretty bad. All because my immune system isn’t sure that the peanut isn’t a bad guy.
Okay, this makes a lot of sense to me, but I still want to know why my antibodies can’t figure out the difference between a peanut and a parasite when someone else’s can.
Source information from http://news.sciencemag.org/evolution/2015/10/got-allergies-blame-parasites?utm_campaign=email-sci-toc&et_rid=17102601&et_cid=68363